U.S. patent application number 12/760366 was filed with the patent office on 2010-08-05 for 2-terminal semiconductor device using abrupt metal-insulator transition semiconductor material.
Invention is credited to Byung Gyu Chae, Kwang Yong Kang, Gyungock Kim, Hyun Tak KIM, Seong Hyun Kim, Yong Sik Lim, Sunglyul Maeng, Doo Hyeb Youn.
Application Number | 20100193824 12/760366 |
Document ID | / |
Family ID | 34930913 |
Filed Date | 2010-08-05 |
United States Patent
Application |
20100193824 |
Kind Code |
A1 |
KIM; Hyun Tak ; et
al. |
August 5, 2010 |
2-TERMINAL SEMICONDUCTOR DEVICE USING ABRUPT METAL-INSULATOR
TRANSITION SEMICONDUCTOR MATERIAL
Abstract
Provided is a 2-terminal semiconductor device that uses an
abrupt MIT semiconductor material layer. The 2-terminal
semiconductor device includes a first electrode layer, an abrupt
MIT semiconductor organic or inorganic material layer having an
energy gap less than 2 eV and holes in a hole level disposed on the
first electrode layer, and a second electrode layer disposed on the
abrupt MIT semiconductor organic or inorganic material layer. An
abrupt MIT is generated in the abrupt MIT semiconductor material
layer by a field applied between the first electrode layer and the
second electrode layer.
Inventors: |
KIM; Hyun Tak;
(Daejeon-city, KR) ; Youn; Doo Hyeb;
(Daejeon-city, KR) ; Chae; Byung Gyu;
(Daejeon-city, KR) ; Kang; Kwang Yong;
(Daejeon-city, KR) ; Lim; Yong Sik;
(Chungcheongbuk-do, KR) ; Kim; Gyungock; (Seoul,
KR) ; Maeng; Sunglyul; (Chungcheongbuk-do, KR)
; Kim; Seong Hyun; (Daejeon-city, KR) |
Correspondence
Address: |
BLAKELY SOKOLOFF TAYLOR & ZAFMAN LLP
1279 OAKMEAD PARKWAY
SUNNYVALE
CA
94085-4040
US
|
Family ID: |
34930913 |
Appl. No.: |
12/760366 |
Filed: |
April 14, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11011878 |
Dec 13, 2004 |
7728327 |
|
|
12760366 |
|
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|
|
Current U.S.
Class: |
257/98 ; 257/79;
257/E33.061; 257/E33.064 |
Current CPC
Class: |
H01L 45/1625 20130101;
H01L 45/04 20130101; H01L 45/14 20130101; H01L 45/1226 20130101;
H01L 45/146 20130101; H01L 45/1233 20130101; H01L 45/147 20130101;
H01L 45/148 20130101 |
Class at
Publication: |
257/98 ; 257/79;
257/E33.061; 257/E33.064 |
International
Class: |
H01L 33/00 20100101
H01L033/00; H01L 33/40 20100101 H01L033/40 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 15, 2004 |
KR |
2004-55096 |
Claims
1. An abrupt metal-insulator transition (MIT) semiconductor
material layer having a semiconductor energy gap and an impurity
level (a hole or an electron), generating an abrupt MIT from an
insulator to metal at a predetermined voltage, and emitting light
according to an application of a voltage.
2. The abrupt MIT semiconductor material layer of claim 1, wherein
the abrupt MIT semiconductor material layer has a peak of
photo-luminescence (PL) at a wavelength corresponding to the energy
gap by irradiating a laser beam, and the intensity of the peak of
PL is reduced by the abrupt MIT, and the intensity of PL
corresponding to a wavelength below the peak of PL increases.
3. The abrupt MIT semiconductor material layer of claim 1, wherein
the abrupt MIT semiconductor material layer comprises p-type
semiconductor elements (group type III-V and II-VI).
4. The abrupt MIT semiconductor material layer of claim 3, wherein
the abrupt MIT semiconductor material layer comprises p-type
GaAs.
5. The abrupt MIT semiconductor material layer of claim 1, wherein
the abrupt MIT semiconductor material layer comprises n-type
semiconductor elements (group type III-V and II-VI).
6. The abrupt MIT semiconductor material layer of claim 1, wherein
the abrupt MIT semiconductor material layer is used in at least one
of a light emitting diode (LED), a light emitting device, and an
accelerator for discharging light.
7. A light emitting device comprising: a substrate; the abrupt MIT
semiconductor material layer of claim 1 disposed on the substrate;
and a first electrode layer and a second electrode layer facing
each other on the abrupt MIT semiconductor material layer and
spaced apart from each other.
8. The light emitting device of claim 7, wherein the abrupt MIT
semiconductor material layer comprises p-type semiconductor
elements (group type III-V and II-VI).
9. The light emitting device of claim 7, wherein the abrupt MIT
semiconductor material layer comprises n-type semiconductor
elements (group type III-V and II-VI).
10. The light emitting device of claim 7, wherein the abrupt MIT
semiconductor material layer is used in at least one of an LED, a
light emitting device, and an accelerator for discharging
light.
11. The light emitting device of claim 7, further comprising: a
buffer layer disposed between the substrate and the abrupt MIT
semiconductor material layer.
12. The light emitting device of claim 7, wherein the first
electrode layer has a structure in which an electrode is disposed
in the left of the abrupt MIT semiconductor material layer and
partially covers a part of an upper portion of a semiconductor, and
the second electrode layer has the same structure as the first
electrode layer except that an electrode is disposed in the right
of the abrupt MIT semiconductor material layer.
13. A light emitting device comprising: a substrate; a first
electrode layer disposed on the substrate; the abrupt MIT
semiconductor material layer of claim 1 disposed on the first
electrode layer; and a second electrode layer disposed on the
abrupt MIT semiconductor material layer.
14. The light emitting device of claim 13, wherein the substrate
comprises sapphire, Si, GaAs, and a metal board.
15. The light emitting device of claim 13, further comprising: a
buffer layer disposed between the substrate and the first electrode
layer.
16. The light emitting device of claim 13, wherein the abrupt MIT
semiconductor material layer comprises p-type semiconductor
elements (group type III-V and II-VI).
17. The light emitting device of claim 13, wherein the abrupt MIT
semiconductor material layer comprises n-type semiconductor
elements (group type III-V and II-VI).
18. The light emitting device of claim 13, wherein the second
electrode layer comprises an indium tin oxide (ITO) transparent
electrode.
19. The light emitting device of claim 13, further comprising: a
buffer layer disposed between the substrate and the first electrode
layer, wherein the second electrode layer is a transparent
electrode and covers an entire surface of an upper portion of the
abrupt MIT semiconductor material layer.
Description
[0001] This application claims the priority of Korean Patent
Application No. 2004-55096, filed on Jul. 15, 2004, in the Korean
Intellectual Property Office, the disclosure of which is
incorporated herein in its entirety by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a semiconductor device and
a method of manufacturing the same, and more particularly, to a
2-terminal semiconductor device that uses an abrupt metal-insulator
transition (MIT) semiconductor material and a method of
manufacturing the same.
[0004] 2. Description of the Related Art
[0005] Recently, a memory device using a structural phase
transition material has drawn interest and research and development
regarding this memory device has been actively performed. An
example of the memory device using a structural phase material has
been disclosed in U.S. Pat. No. 5,687,112. The memory device
disclosed is a phase change memory (PCM) device that uses a
crystalline phase and an amorphous phase occurring at a high
temperature. This device can be used as a memory device since it
can use a phase change according to the structural phase
transition. However, the device cannot be used for other
applications, such as a switching device, because a rapid switching
speed cannot be implemented due to the location change of atoms
according to the structural phase transition. If a rapid switching
speed is forced, the memory device may break due to a hysteresis
phenomenon. A drawback of the phase change memory device is its
limited applications.
[0006] On the other hand, a consecutive metal-insulator transistor,
that is, a Mott-Hubbard field transistor which uses a Mott-Hubbard
insulator in an insulator that allows a second transition has been
suggested as a semiconductor device that uses a metal-insulator
transition. The Mott-Hubbard field transistor has been disclosed by
D. M. Newns, J. A. Misewich, C. C. Tsuei, A. Gupta, B. A. Scott, A.
Schrott, in Appl. Phys. Lett. 73 (1998) 780. The Mott-Hubbard field
transistor performs an ON/OFF operation according to the
metal-insulator transition. Unlike the conventional MOS field
transistor, the integration density of this transistor can be
significantly improved since a depletion layer does not exist.
Also, the Mott-Hubbard field transistor has higher speed switching
characteristic than the MOS field transistor. However, charges to
be used for carriers must be added until the Mott-Hubbard field
transistor reaches the characteristic of a metal since Mott-Hubbard
field transistor uses MIT that is consecutively generated.
Accordingly, the charges added must have high concentration, and a
dielectric constant of a gate insulating layer must be high, the
thickness of the gate insulating layer must be thin, and a gate
voltage applied must be greater than the high concentration of the
added charge. However, if the dielectric constant is too high, the
lifetime of the transistor is reduced since the fatigue
characteristic of the dielectric may go badly at a high switching
speed. There is a process limit to make a thin insulator. Also,
when the gate voltage is high, there is a drawback of high power
consumption.
[0007] To solve these problems, a switching field transistor that
uses an abrupt MIT semiconductor material, not a consecutive
transition, has been disclosed in U.S. Pat. No. 6,624,463. The
abrupt MIT semiconductor material has a characteristic in that a
transition from an insulator to a metal takes place rapidly not
consecutively by adding a low concentration of holes to a
Mott-Brinkman-Rice insulator. The Hole-driven metal-insulator
transition theory has been disclosed in the article "New Trends in
Superconductivity" by Hyun-Tak Kim published in NATO Science Series
Vol II/67 (Kluwer, 2002) pp. 137 and at the web address
http://xxx.lanl.gow/abs/cond-mat/0110112. Hyun-Tak Kim, Byung-Gyu
Chae, Doo-Hyeb Youn, Sung-Lyul Maeng, Gyungock Kim, Kwang-Yong
Kang, and Yong-Sik Lim in New Journal of Physics 6 (2004) 52 has
also disclosed a research about the abrupt MIT by using vanadium
dioxide (VO.sub.2) which is a representative Mott-Brinkman-Rice
insulator. The problems of the field transistor using the
consecutive metal-insulator transition material are solved in the
switching field transistor since the concentration of the holes
added is very low. However, the availability of the abrupt MIT
semiconductor materials is limited and the cost of forming an
abrupt MIT semiconductor material layer is high.
SUMMARY OF THE INVENTION
[0008] The present invention provides a 2-terminal semiconductor
device that uses an abrupt MIT semiconductor material that can be
formed readily with a low cost without generating a structural
phase transition.
[0009] The present invention also provides a method of
manufacturing a 2-terminal semiconductor device that uses an abrupt
MIT semiconductor material.
[0010] The semiconductor in the present invention is a material
having an energy gap less than 2 eV and a hole level or an
electronic level and acting as an insulator at low temperatures.
The hole level denotes that the material has holes and the
electronic level denotes that the material has electrons, and the
material includes organic and inorganic materials.
[0011] According to an aspect of the present invention, there is
provided a 2-terminal semiconductor device comprising: a first
electrode layer as a substrate, an abrupt MIT organic or inorganic
semiconductor material layer disposed on the first electrode, and a
second electrode layer disposed on the abrupt MIT organic or
inorganic semiconductor material layer.
[0012] The abrupt MIT semiconductor material layer can include an
individual p-type semiconductor of Si, Ge, Al, As, Sb, B, N, Ga, P,
In, Te, Ag, Cd, Zn, Pb, S, Bi, K, H, Be, O or C to which a low
concentration of holes is added or a compound semiconductor
composed of these elements.
[0013] The abrupt MIT semiconductor material layer can include an
individual p-type semiconductor of Y, Pr, Ba, Cu, La, Sr, Ti, V,
Ca, Fe, W, Mo, Nb, Al, Hf, Ta, Zr, La, Bi, Pd, or O to which a low
concentration of holes is added or a compound semiconductor
composed of these elements.
[0014] The abrupt MIT semiconductor material layer can include an
individual p-type semiconductor of Fe, S, Sm, Se, Te, Eu, Si, Mn,
Co, B, H, Li, Ca, Y, Ru, Os, P, As, P, Ir, Ti, Zr, Hf, Mo, Te, Tc,
Re, Rh, Pt, Yb, B, O or C, transition elements, earth elements, and
lanthanides to which a low concentration of holes is added or a
compound semiconductor composed of these elements.
[0015] The abrupt MIT semiconductor material layer may include
inorganic compound semiconductors that include p-type
semiconductors to which a low concentration of holes is added,
p-type oxide semiconductors to which a low concentration of hole is
added, p-type semiconductor elements (III-V and II-VI family) to
which a low concentration of holes is added, transition metal
elements, earth elements, lanthanides, p-type organic semiconductor
to which a low concentration of holes is added, and insulators.
[0016] The p-type semiconductor to which a low concentration of
holes is added can include Si(100), Si(111), Si(110), Si:B, Si:P,
Ge(100), SIC, SiGe, AlAs, InAlAs, AlSb, BN, GaAs, InGaAs, GaP,
GaSb, Ga.sub.xSb.sub.1-x (0.ltoreq.x.ltoreq.0.5),
Ge.sub.xSb.sub.1-x (0.ltoreq.x.ltoreq.0.2), InN, InAs, InP, InSb,
In.sub.xSb.sub.1-x (0.ltoreq.x.ltoreq.0.5),
Ge.sub.aIn.sub.bSb.sub.cTe.sub.d (0.ltoreq.a.ltoreq.0.2,
0.ltoreq.b.ltoreq.0.2, 0.55.ltoreq.c.ltoreq.1,
0.ltoreq.d.ltoreq.0.5), In.sub.xSb.sub.yTe.sub.z
(0.ltoreq.x.ltoreq.0.2, 0.5.ltoreq.y.ltoreq.1,
0.ltoreq.z.ltoreq.0.3), Ag.sub.aIn.sub.bSb.sub.cTe.sub.d
(0.ltoreq.a.ltoreq.0.2, 0.ltoreq.b.ltoreq.0.2,
0.5.ltoreq.c.ltoreq.1, 0.ltoreq.d.ltoreq.0.5),
Te.sub.aGe.sub.bSn.sub.cAu.sub.d (0.5.ltoreq.a.ltoreq.1,
0.ltoreq.b.ltoreq.0.2, 0.ltoreq.c.ltoreq.0.3,
0.ltoreq.d.ltoreq.0.5), AgSbTe.sub.2, AgInTe.sub.2, GeCdS, CdSe,
CdTe, ZnS, ZnSe, ZnTe, PbS, PbSe, PbTe, Grey Sn, Grey Se, Sb, Te,
Sb.sub.1-xTe.sub.x (0.ltoreq.x.ltoreq.0.5), B, DAC (Diamondlike
Amorphous-C), TAC (Tetrahedral Amorphous-C):N, a-C; H (Amorphous
hydrogenated carbon layers, or DLC (Diamond-Like Carbon),
K.sub.4C.sub.60, K.sub.6C.sub.60, Ga--As--Si system, Ga--GaAs--Ge
system, Ga--GaAs--Sn, Ga--As--Sn system, Ga--As--Zn system,
Ga--P--Si system, Ga--P--Zn system, Ga--P--Ge system, GaP--Bi
system, GeTe--Bi.sub.2Te.sub.3, GeSb.sub.2Te.sub.4, GaP:N, GaAs:Ca,
GaAs:K, GaAs:Cl, or GeBi.sub.2Te.sub.4.
[0017] The p-type oxide semiconductor to which a low concentration
of holes is added can include
Y.sub.1-xPr.sub.xBa.sub.2Cu.sub.3O.sub.7 (0.ltoreq.x.ltoreq.1),
La.sub.2Sr.sub.xCuO.sub.4 (0.ltoreq.x.ltoreq.1),
La.sub.2-xBa.sub.xCuO.sub.4 (0.ltoreq.x.ltoreq.1),
Ba.sub.1-xSrTiO.sub.3 (0.ltoreq.x.ltoreq.1), La.sub.1-xSrTiO.sub.3
(0.ltoreq.x.ltoreq.1), VO.sub.2, V.sub.2O.sub.3,
Ca.sub.xV.sub.1-xO.sub.2 (0.ltoreq.x.ltoreq.1),
Al.sub.xV.sub.1-xO.sub.2 (0.ltoreq.x.ltoreq.1),
Ti.sub.xV.sub.1-xO.sub.2 (0.ltoreq.x.ltoreq.1),
Fe.sub.xV.sub.1-xO.sub.2 (0.ltoreq.x.ltoreq.1),
W.sub.xV.sub.1-xO.sub.2 (0.ltoreq.x.ltoreq.1),
Mo.sub.xV.sub.1-xO.sub.2 (0.ltoreq.x.ltoreq.1), Fe.sub.3O.sub.4,
Nb.sub.2O.sub.5, WO.sub.3, Ti.sub.2O.sub.3, PdO, Al.sub.2O.sub.3,
HfO.sub.2, SiO.sub.2, Y.sub.2O.sub.3, Ta.sub.2O.sub.5, TiO.sub.2,
or ZrO.sub.2.
[0018] The p-type transition metal to which a low concentration of
holes is added and semiconductor that includes the transition
metals can include Fe.sub.1-xS (0.ltoreq.x.ltoreq.0.5), SmS, SmSe,
SmTe, Eu.sub.3S.sub.4, FeSi.sub.2, Fe.sub.1-xMn.sub.xSi.sub.2
(0.ltoreq.x.ltoreq.0.5), Fe.sub.1-xCo.sub.xSi.sub.2
(0.ltoreq.x.ltoreq.0.5), B:H(9%), B:H(11%), B:H(24%), LiAlB1.sub.4,
CuB.sub.4, CaB.sub.6, a-AlB1.sub.2, YB.sub.66, SmB.sub.66,
Mn.sub.11Si.sub.19, Mn.sub.26Si.sub.45, Mn.sub.15Si.sub.26,
Ru.sub.2Si.sub.3, Fe.sub.2Si.sub.2, RuP.sub.2, RuPAs, RuAs.sub.2,
OsP.sub.2, OsAs.sub.2, RhP.sub.2, RhAs.sub.2, IrP.sub.2,
IrAs.sub.2, RuP.sub.4, FeAs, RuAsS, OsPS, OsAsS, OsPSe,
Ti.sub.1+xS.sub.2 (0.ltoreq.x.ltoreq.0.5), TiS.sub.3-x
(0.ltoreq.x.ltoreq.0.5), Zr.sub.1+xSe.sub.2
(0.01.ltoreq.x.ltoreq.0.1), Zr.sub.2S.sub.3, ZrSe.sub.3,
HfSe.sub.2, MoS.sub.2, 2H-MoTe.sub.2-x (0.01.ltoreq.x.ltoreq.0.1),
2H--WSe.sub.2, MnTe, TcS.sub.2, TcSe.sub.2, ReS.sub.2, ReSe.sub.2,
FeS.sub.2, RuS.sub.2, RuSe.sub.2, RhS.sub.3, RhSe.sub.2,
RhSe.sub.3, IrS.sub.2, IrSe.sub.2, PtS, PtxS.sub.2
(0.95.ltoreq.x.ltoreq.1), SmTe, EuTe, YbSe, YbTe or BC.
[0019] The p-type organic semiconductor to which a low
concentration of holes is added can be a D.sup.+A.sup.- type in
which D.sup.+ is an organic donor and A.sup.- is an organic
acceptor.
[0020] In this case, the D.sup.+A.sup.- type can include
D.sup.+A.sup.-=TTF+Br, D.sup.+A.sup.-=BEDT-TTF, or
D.sup.+A.sup.-=TMPD+TCNQ, wherein TTF is tetrathiofulvalene,
BEDT-TTF is bis-ethylenedithio-tetrathiofulvalene, TMPD is
N,N,N',N'-tetramethyl-p-phenylenediamine, and TCNQ is
tetracyano-p-quinodimethane, and the TCNQ is an active component
that is switching between the TCNQ- and TCNQ by injecting
holes.
[0021] Also, the p-type organic semiconductor may include pentacene
and its derivatives, thiophene and thiophene oligomer,
benzodithiophene dimer, phthalocyanine, Poly(alkyl-thiophene),
Poly(3-hexylyl-thiophene), Poly(3-octyl-thiophene),
Poly(3-dodecyl-thiophene), anthradithiophene (ADT), dihexyl-ADT,
didodecyl-ADT, thiophene derivatives that includes dioctadecyl-ADT,
or aromatic compound.
[0022] The first electrode layer and the second electrode layer can
include W, Mo, Au/Cr, Ti/W, Ti/Al/N, Ni/Cr, Al/Au, Pt, Cr/Mo/Au,
YBa.sub.2Cu.sub.3O.sub.7-d, or Ni/Mo/Au.
[0023] The 2-terminal semiconductor device can further comprise a
resistance unit that is connected to at least one of the first
electrode layer and the second electrode layer.
[0024] According to another aspect of the present invention, there
is provided a 2-terminal semiconductor device comprising: a
substrate, a first electrode layer disposed on the substrate, an
abrupt MIT semiconductor material layer disposed on the first
electrode layer, and a second electrode layer disposed on the
abrupt MIT semiconductor material layer.
[0025] The substrate can include a SOI (silicon on insulator), Si,
SiO.sub.2, GaAs, GaSb, InP, Al.sub.3O.sub.4, plastic, glass,
V.sub.2O.sub.5, PrBa.sub.2Cu.sub.3O.sub.7,
YBa.sub.2Cu.sub.3O.sub.7, MgO, SrTiO.sub.3, Nb-doped SrTiO.sub.3 or
an insulator.
[0026] A buffer layer disposed between the substrate and the first
electrode layer may be further included.
[0027] In this case, the buffer layer can include a SiO.sub.2 layer
or a Si.sub.3N.sub.4 layer.
[0028] The 2-terminal semiconductor device may further comprise a
resistance unit that is connected to at least one of the first
electrode layer and the second electrode layer.
[0029] According to another aspect of the present invention, there
is provided a 2-terminal semiconductor device comprising: a
substrate, a first electrode layer disposed on the substrate, an
abrupt MIT semiconductor material layer disposed on the first
electrode layer, a second electrode layer disposed on the abrupt
MIT semiconductor material layer, and a gate insulating layer
disposed at least one of both surfaces of the abrupt MIT
semiconductor material layer.
[0030] According to another aspect of the present invention, there
is provided a 2-terminal semiconductor device comprising a
substrate, a first electrode layer disposed on the substrate, an
abrupt MIT semiconductor material layer disposed on the first
electrode layer, a second electrode layer disposed on the abrupt
MIT semiconductor material layer, and a ferromagnetic thin layer
disposed at least one of both surfaces of the abrupt MIT
semiconductor material layer.
[0031] According to another aspect of the present invention, there
is provided a 2-terminal semiconductor device comprising a
substrate, an abrupt MIT semiconductor material layer disposed on
the substrate, and a first electrode layer and a second electrode
layer disposed apart facing each other on the abrupt MIT
semiconductor material layer.
[0032] The 2-terminal semiconductor device may further comprise a
buffer layer disposed between the substrate and the abrupt MIT
semiconductor material layer.
[0033] The 2-terminal semiconductor device may further comprise a
resistance unit that is connected to at least one of the first
electrode layer and the second electrode layer.
[0034] The first electrode layer and the second electrode layer can
be formed in a finger shape.
[0035] According to another aspect of the present invention, there
is provided a 2-terminal semiconductor device comprising a
substrate, an abrupt MIT semiconductor material layer disposed on
the substrate, a first electrode layer and a second electrode layer
disposed from and facing each other on the abrupt MIT semiconductor
material layer, and a gate insulating layer disposed on the abrupt
MIT semiconductor material layer between the first electrode layer
and the second electrode layer.
[0036] According to another aspect of the present invention, there
is provided a 2-terminal semiconductor device comprising: a
substrate, an abrupt MIT semiconductor material layer disposed on
the substrate, a first electrode layer and a second electrode layer
disposed apart facing each other on the abrupt MIT semiconductor
material layer, and a ferromagnetic thin layer disposed on the
abrupt MIT semiconductor material layer between the first electrode
layer and the second electrode layer.
[0037] According to another aspect of the present invention, there
is provided a method of manufacturing a 2-terminal semiconductor
device, comprising: forming a first electrode layer on a substrate,
forming an abrupt MIT semiconductor material layer disposed on the
first electrode layer, and forming a second electrode layer on the
abrupt MIT semiconductor material layer.
[0038] The forming of the first electrode layer and the second
electrode layer can be performed by a sputtering method.
[0039] The forming of the abrupt MIT semiconductor material layer
can be performed by using a pulse laser method.
[0040] The forming of the abrupt MIT semiconductor material layer
can be performed by using a molecular beam epitaxy method.
[0041] The method may further comprise forming a buffer layer on
the substrate before forming the abrupt MIT semiconductor material
layer.
[0042] According to another aspect of the present invention, there
is provided a method of manufacturing a 2-terminal semiconductor
device, comprising forming an abrupt MIT semiconductor material
layer on a substrate, forming a metal layer on the abrupt MIT
semiconductor material layer, and forming a first electrode layer
and a second electrode layer disposed to face each other and having
an exposed surface therebetween after exposing a portion of the
abrupt MIT semiconductor material layer by patterning the metal
layer.
[0043] The method may further comprise forming a buffer layer on
the substrate before forming the abrupt MIT semiconductor material
layer.
BRIEF DESCRIPTION OF THE DRAWINGS
[0044] The above and other features and advantages of the present
invention will become more apparent by describing in detail
exemplary embodiments thereof with reference to the attached
drawings in which:
[0045] FIG. 1 is a cross-sectional view illustrating a 2-terminal
semiconductor device that uses an abrupt MIT semiconductor material
according to an embodiment of the present invention;
[0046] FIG. 2 is a cross-sectional view illustrating a 2-terminal
semiconductor device that uses an abrupt MIT semiconductor material
according to another embodiment of the present invention;
[0047] FIG. 3 is a 2-terminal network circuit diagram including a
2-terminal semiconductor device that uses an abrupt MIT
semiconductor material according to the present invention;
[0048] FIG. 4 is a graph showing an effect of hole doping in the
abrupt MIT semiconductor material of FIGS. 1 and 2;
[0049] FIG. 5 is a graph showing the existence of a sub-gap less
than 2 eV in the abrupt MIT semiconductor material of FIGS. 1 and
2;
[0050] FIG. 6 is a graph for explaining the change of carriers
according to temperature in the abrupt MIT semiconductor material
of FIGS. 1 and 2;
[0051] FIG. 7 is a graph showing the change of resistance according
to temperature in the abrupt MIT semiconductor material of FIGS. 1
and 2;
[0052] FIG. 8 is a graph showing the test results of Raman
scattering for observing the structural change of a material
according to temperature change;
[0053] FIG. 9 is a graph showing the test results of micro Raman
scattering with respect to the abrupt MIT semiconductor material of
FIGS. 1 and 2 for observing the structural change of a material
according to current change;
[0054] FIG. 10 is a graph showing the characteristic of
voltage-current of the abrupt MIT semiconductor material of FIGS. 1
and 2 according to temperature change;
[0055] FIG. 11 is a graph showing the voltage-current
characteristic in the 2-terminal network circuit of FIG. 3;
[0056] FIG. 12 is a graph showing the hysteresis characteristic of
a metal state of the abrupt MIT semiconductor material of FIGS. 1
and 2.
[0057] FIG. 13 is a graph showing the voltage-current
characteristic in a 2-terminal semiconductor device that uses a
vanadium dioxide layer as an abrupt MIT semiconductor material;
[0058] FIG. 14 is a graph showing the voltage-current
characteristic in a 2-terminal semiconductor device that uses
p-type gallium (Ga) arsenic (As) as an abrupt MIT semiconductor
material;
[0059] FIG. 15 is a graph showing the voltage-current
characteristic in a 2-terminal semiconductor device that uses
p-type GaAs as an abrupt MIT semiconductor material;
[0060] FIG. 16 is a graph showing the voltage-current
characteristic according to temperature change in a 2-terminal
semiconductor device that uses p-type GaAs as an abrupt MIT
semiconductor material;
[0061] FIG. 17 is a graph showing the hysteresis characteristic of
a metal phase of p-type GaAs as an abrupt MIT semiconductor
material;
[0062] FIGS. 18A and 18B are graphs showing the temperature
dependence of electric conductivity of GaAs and that of the
resistance of a p-type GaAs thin layer in which a low concentration
of holes are added, respectively;
[0063] FIG. 19 is a graph showing the photocurrent characteristic
measured using Ar ion laser of 514.5 nm in a 2-terminal
semiconductor device that uses p-type GaAs as an abrupt MIT
material;
[0064] FIG. 20 is a graph of spectrum showing the intensity and
wave dependence of fluorescent light emitted from a 2-terminal
semiconductor device manufactured that uses p-type GaAs as an
abrupt MIT semiconductor material by irradiating an Ar laser having
a wavelength of 488 nm.
[0065] FIG. 21 is a graph showing a current-voltage characteristic
measured by a current-control method that measures voltage by
flowing current in a 2-terminal device that uses p-type GaAs as an
abrupt MIT material;
[0066] FIG. 22 is a perspective view illustrating an example of an
electrode shape of the 2-terminal semiconductor device in FIG. 2;
and
[0067] FIGS. 23A and 23B are a perspective view of an abrupt MIT
semiconductor material and a graph showing a relationship-type of
length and width according to the thickness change of the abrupt
MIT semiconductor material of FIGS. 1 and 2, respectively.
DETAILED DESCRIPTION OF THE INVENTION
[0068] The present invention will now be described more fully with
reference to the accompanying drawings in which exemplary
embodiments of the invention are shown. However, this invention may
be embodied in many different forms and should not be construed as
being limited to the embodiments set forth herein.
[0069] FIG. 1 is a cross-sectional view illustrating a 2-terminal
semiconductor device 100 that uses an abrupt MIT semiconductor
material according to an embodiment of the present invention.
[0070] Referring to FIG. 1, the 2-terminal semiconductor device 100
has a stacking structure in which a current flows in a vertical
direction and includes sequentially stacked a buffer layer 120, a
first electrode layer 141, an abrupt MIT semiconductor material
layer 130, and a second electrode layer 142 on a substrate 110. In
some cases, the substrate 110, the buffer layer 120, and the first
electrode layer 141 can be formed of a single layer. In this case,
the first electrode layer 141 acts as a substrate without the
substrate 110 and the buffer layer 120. Also, in some cases, a gate
insulating layer or a ferromagnetic thin layer can be disposed at
least one of the both surfaces of the abrupt MIT semiconductor
material layer 130.
[0071] There is no specific limitation of materials for forming the
substrate 110 and can be formed of Si, SiO.sub.2, GaAs,
Al.sub.3O.sub.4, plastics, glass, V.sub.2O.sub.5,
PrBa.sub.2Cu.sub.3O.sub.7, YBa.sub.2Cu.sub.3O.sub.7, MgO,
SrTiO.sub.3, SrTiO.sub.3 doped with Nb, or Silicon-On-Insulator
(SOI). The buffer 120 is disposed on the substrate 110 for well
growing the first electrode layer 141, but it can be omitted in
some cases. The buffer layer 120 is formed of a material that can
control a lattice constant of the substrate 110 and the first
electrode layer 141 and can be formed of a SiO.sub.2 layer or a
Si.sub.3N.sub.4 layer.
[0072] The abrupt MIT semiconductor material layer 130 denotes a
thin layer formed of a semiconductor material wherein an abrupt MIT
can take place when holes in a low concentration are added. Here,
the low hole concentration n is given approximately
(0.2/a.sub.H).sup.3 in the consideration of the Mott criterion,
where a.sub.H is Bohr radius of a material. For example, the hole
concentration n of a vanadium oxide layer VO.sub.2 having an energy
gap of 0.6 eV and a hole level is approximately 0.0018%, that is,
n.apprxeq.3.times.10.sup.18 cm.sup.-3. The abrupt MIT semiconductor
material layer 130, such as the VO.sub.2 layer, is formed of a
material having an energy gap of less than 2 eV and hole in the
hole level. As another example, the hole concentration n of p-type
GaAs having an energy gap of 1.45 and a hole level is approximately
n.apprxeq.0.001%, that is, n.apprxeq.1.times.10.sup.14 cm.sup.-3.
The theory of hole-driven metal-insulator transition by adding a
low concentration of holes has disclosed in the article of "New
Trends in Superconductivity" by Hyun-Tak Kim published in NATO
Science Series Vol II/67 (Kluwer, 2002) p 137 or
http://xxx.lanl.gov/abs/cond-mat/0110112. The resultant equation is
show in FIG. 4. Here, the hole level denotes an energy level in
which the holes exist in a constraint state. A n-type semiconductor
with a high resistance can also be used as the abrupt MIT
semiconductor material layer 130.
[0073] The abrupt MIT semiconductor material layer 130 includes
p-type semiconductor Si, Ge, Al, As, Sb, B, N, Ga, P, In, Te, Ag,
Cd, Zn, Pb, S, Bi, K, H, Be, O or C to which a low concentration of
holes is added, an individual element, or p-type compound
semiconductors composed of these elements. The abrupt MIT
semiconductor material layer 130 also includes p-type oxide
semiconductor to which a low concentration of holes are added, such
as the elements of Y, Pr, Ba, Cu, La, Sr, Ti, V, Ca, Fe, W, Mo, Nb,
Al, Hf, Ta, Zr, La, Pd, O and oxide semiconductor composed of these
elements, and Fe, S, Sm, Se, Te, Eu, Si, Mn, Co, B, H, Li, Ca, Y,
Ru, Os, P, As, P, Ir, Ti, Zr, Hf, Mo, Te, Tc, Re, Rh, Pt, Yb, Ce,
Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Lu, O or elements of C,
rare earth, and lanthanide, or compound semiconductors composed of
these elements.
[0074] When classified in a different manner, the abrupt MIT
semiconductor material layer 130 includes inorganic compound
semiconductors that include a p-type semiconductor to which a low
concentration of holes is added, a p-type oxide semiconductor to
which a low concentration of holes is added, p-type semiconductor
elements (III-V and II-V family), transition metal elements, earth
elements, and lanthanide elements to which a low concentration of
holes are added or p-type organic semiconductor and insulator to
which a low concentration of holes are added.
[0075] The p-type semiconductors to which a very low concentration
of holes is added include Si(100), Si(111), Si(110), Si:B, Si:P,
Ge(100), SiC, SiGe, AlAs, InAlAs, AlSb, BN, GaAs, InGaAs, GaP,
GaSb, Ga.sub.xSb.sub.1-x (0.ltoreq.x.ltoreq.0.5),
Ge.sub.xSb.sub.1-x (0.ltoreq.x.ltoreq.0.2), InN, InAs, InP, InSb,
In.sub.xSb.sub.1-x (0.ltoreq.x.ltoreq.0.5),
Ge.sub.aIn.sub.bSb.sub.cTe.sub.d (0.ltoreq.a.ltoreq.0.2,
0.ltoreq.b.ltoreq.0.2, 0.5.ltoreq.c.ltoreq.1,
0.ltoreq.d.ltoreq.0.5), In.sub.xSb.sub.yTe.sub.z
(0.ltoreq.x.ltoreq.0.2, 0.5.ltoreq.y.ltoreq.1,
0.ltoreq.z.ltoreq.0.3), Ag.sub.aIn.sub.bSb.sub.cTe.sub.d
(0.ltoreq.a.ltoreq.0.2, 0.ltoreq.b.ltoreq.0.2,
0.5.ltoreq.c.ltoreq.1, 0.ltoreq.d.ltoreq.0.5),
Te.sub.aGe.sub.bSnAu.sub.d (0.5.ltoreq.a.ltoreq.1,
0.ltoreq.b.ltoreq.0.2, 0.ltoreq.c.ltoreq.0.3,
0.ltoreq.d.ltoreq.0.5), AgSbTe.sub.2, AgInTe.sub.2, GeCdS, CdSe,
CdTe, ZnS, ZnSe, ZnTe, PbS, PbSe, PbTe, Grey Sn, Grey Se, Sb, Te,
Sb.sub.1-xTe.sub.x (0.ltoreq.x.ltoreq.0.5), B, DAC (Diamondlike
Amorphous-C), TAC (Tetrahedral Amorphous-C):N, a-C; H (Amorphous
hydrogenated carbon layers, or DLC (Diamond-Like Carbon),
K.sub.4C.sub.60, K.sub.6C.sub.60, Ga--As--Si system, Ga--GaAs--Ge
system, Ga--GaAs--Sn, Ga--As--Sn system, Ga--As--Zn system,
Ga--P--Si system, Ga--P--Zn system, Ga--P--Ge system, GaP--Bi
system, GeTe--Bi.sub.2Te.sub.3, GeSb.sub.2Te.sub.4, GaP:N, GaAs:Ca,
GaAs:K, GaAs:Cl, or GeBi.sub.2Te.sub.4.
[0076] The p-type oxide semiconductors to which a very low
concentration of holes are added include
Y.sub.1-xPr.sub.xBa.sub.2Cu.sub.3O.sub.7 (0.ltoreq.x.ltoreq.1),
La.sub.2-xSr.sub.xCuO.sub.4 (0.ltoreq.x.ltoreq.1),
La.sub.2-xBa.sub.xCuO.sub.4 (0.ltoreq.x.ltoreq.1),
Ba.sub.1-xSrTiO.sub.3 (0.ltoreq.x.ltoreq.1), La.sub.1-xSrTiO.sub.3
(0.ltoreq.x.ltoreq.1), VO.sub.2, V.sub.2O.sub.3,
Ca.sub.xV.sub.1-xO.sub.2 (0.ltoreq.x.ltoreq.1),
Al.sub.xV.sub.1-xO.sub.2 (0.ltoreq.x.ltoreq.1),
Ti.sub.xV.sub.1-xO.sub.2 (0.ltoreq.x.ltoreq.1),
Fe.sub.xV.sub.1-xO.sub.2 (0.ltoreq.x.ltoreq.1),
W.sub.xV.sub.1-xO.sub.2 (0.ltoreq.x.ltoreq.1),
Mo.sub.xV.sub.1-xO.sub.2 (0.ltoreq.x.ltoreq.1), Fe.sub.3O.sub.4,
Nb.sub.2O.sub.5, WO.sub.3, Ti.sub.2O.sub.3, PdO, Al.sub.2O.sub.3,
HfO.sub.2, SiO.sub.2, Y.sub.2O.sub.3, Ta.sub.2O.sub.5, TiO.sub.2,
or ZrO.sub.2.
[0077] A semiconductor which includes a p-type transition metal to
which a low concentration of holes is added includes Fe.sub.1-xS
(0.ltoreq.x.ltoreq.0.5), SmS, SmSe, SmTe, Eu.sub.3S.sub.4,
FeSi.sub.2, Fe.sub.1-xMn.sub.xSi.sub.2 (0.ltoreq.x.ltoreq.0.5),
Fe.sub.1-xCo.sub.xSi.sub.2 (0.ltoreq.x.ltoreq.0.5), B:H(9%),
B:H(11%), B:H(24%), LiAlB1.sub.4, CuB.sub.4, CaB.sub.6,
a-AlB1.sub.2, YB.sub.66, SmB.sub.66, Mn.sub.11Si.sub.19,
Mn.sub.26Si.sub.45, Mn.sub.15Si.sub.26, Ru.sub.2Si.sub.3,
Fe.sub.2Si.sub.2, RuP.sub.2, RuPAs, RuAs.sub.2, OsP.sub.2,
OsAs.sub.2, RhP.sub.2, RhAs.sub.2, IrP.sub.2, IrAs.sub.2,
RuP.sub.4, FeAs, RuAsS, OsPS, OsAsS, OsPSe, Ti.sub.1+xS.sub.2
(0.ltoreq.x.ltoreq.0.5), TiS.sub.3-x (0.ltoreq.x.ltoreq.0.5),
Zr.sub.1+xSe.sub.2 (0.01.ltoreq.x.ltoreq.0.1), Zr.sub.2S.sub.3,
ZrSe.sub.3, HfSe.sub.2, MoS.sub.2, 2H-MoTe.sub.2-x
(0.01.ltoreq.x.ltoreq.0.1), 2H--WSe.sub.2, MnTe, TcS.sub.2,
TcSe.sub.2, ReS.sub.2, ReSe.sub.2, FeS.sub.2, RuS.sub.2,
RuSe.sub.2, RhS.sub.3, RhSe.sub.2, RhSe.sub.3, IrS.sub.2,
IrSe.sub.2, PtS, PtxS.sub.2 (0.9.ltoreq.x.ltoreq.1), SmTe, EuTe,
YbSe, YbTe, or BC.
[0078] The p-type organic semiconductor to which a very low
concentration of holes is added is a D.sup.+A.sup.- type in which
D.sup.+ is an organic donor and A.sup.- is an organic acceptor, and
include D.sup.+A.sup.-=TTF+Br, D.sup.+A.sup.-=BEDT-TTF, or
D.sup.+A.sup.-=TMPD+TCNQ. Here, TTF is tetrathiofulvalene, BEDT-TTF
is bis-ethylenedithio-tetrathiofulvalene, TMPD is
N,N,N',N'-tetramethyl-p-phenylenediamine, and TCNQ is
tetracyano-p-quinodimethane. And, the TCNQ is an active component
that switches between the TCNQ- and TCNQ by injecting holes.
[0079] Also, the p-type organic semiconductor includes pentacene
and its derivatives, thiophene and thiophene oligomer,
benzodithiophene dimer, phthalocyanine, Poly(alkyl-thiophene),
Poly(3-hexylyl-thiophene), Poly(3-octyl-thiophene),
Poly(3-dodecyl-thiophene), anthradithiophene (ADT), dihexyl-ADT,
didodecyl-ADT, thiophene derivatives that includes dioctadecyl-ADT,
aromatic compound, or organic compound.
[0080] The first and second electrode layers 141 and 142 include W,
Mo, Au/Cr, Ti/W, Ti/Al/N, Ni/Cr, Al/Au, Pt, Cr/Mo/Au,
YBa.sub.2Cu.sub.3O.sub.7-d, or Ni/Mo/Au.
[0081] The operation of a semiconductor device structure that uses
an abrupt MIT semiconductor material will now be described. When a
predetermined intensity of bias is applied to the first and second
electrode layers 141 and 142, a field of a predetermined magnitude
is formed on both ends of the abrupt MIT semiconductor material
layer 130. Then, a hole doping phenomenon occurs due to the field,
that is, the holes existed in the hole level of the abrupt MIT
semiconductor material layer 130 are injected into a valence band.
The abrupt MIT semiconductor material layer 130 transitions to a
metal from an insulator according to the doping phenomenon, and as
a result, a current flows between the first and the second
electrode layers 141 and 142.
[0082] A method of manufacturing the 2-terminal semiconductor
device 100 that uses an abrupt MIT semiconductor material having a
stacking structure will now be described. First, a buffer layer
120, such as a titanium (Ti) layer, is formed on the semiconductor
substrate 110 such as a silicon substrate, and the first electrode
141 formed of a platinum (Pt) thin layer as a lower electrode is
formed on the buffer layer 120. The Pt thin layer can be formed by
a sputtering method. Next, the abrupt MIT semiconductor material
layer 130 is formed of a VO.sub.2 layer. The VO.sub.2 layer can be
deposited by a pulse laser method. In some cases, the abrupt MIT
semiconductor material layer 130 can be formed by a Molecular Beam
Epitaxy method. Next, the second electrode 142 formed of an Au/Cr
layer is formed on the abrupt MIT semiconductor material layer 130
using a sputtering method.
[0083] FIG. 2 is a cross-sectional view illustrating a 2-terminal
semiconductor device 200 that uses an abrupt MIT semiconductor
material according to another embodiment of the present
invention.
[0084] Referring to FIG. 2, the 2-terminal semiconductor device 200
has a plane structure in which a current flows in a horizontal
direction and has a buffer layer 220 disposed on a substrate 210
and an abrupt MIT semiconductor material layer pattern 230 on the
buffer layer 220. The abrupt MIT semiconductor material layer
pattern 230 is disposed on a portion of a surface of the buffer
layer 220. A first electrode layer 241 and a second electrode layer
242 are disposed by a predetermined distance apart from each other
on the abrupt MIT semiconductor material layer pattern 230. In some
cases, a gate insulating layer or a ferromagnetic thin layer can be
interposed between the first electrode layer 241 and the second
electrode layer 242.
[0085] The operation of the 2-terminal semiconductor device 200
having a plane structure is identical to the operation of the
2-terminal semiconductor device 100 having a stacking structure of
FIG. 1 except the direction of a current flow that is horizontal
due to the transition the abrupt MIT semiconductor material layer
pattern 230 to a metal.
[0086] A method of manufacturing the 2-terminal semiconductor
device 200 that uses an abrupt MIT semiconductor material layer
pattern 230 having a plane structure will now be described. First,
the buffer layer 220 formed of Ti layer is formed on the
semiconductor substrate 210 and the abrupt MIT semiconductor
material layer 130 is formed using a VO.sub.2 layer on the buffer
layer 220. Next, after exposing a portion of a surface of the
buffer layer 220 by patterning the abrupt MIT semiconductor
material layer 130, a metal layer (not shown) is formed on the
entire surface of the buffer layer 220. Afterward, a mask layer
pattern (not shown) is formed on the metal layer and an etching
process using the mask layer pattern removes an exposed portion of
the metal layer. Then, a portion of a surface of the abrupt MIT
semiconductor material layer 130 used as a channel region is
exposed and the first electrode layer 241 and the second electrode
layer 242 are formed on both sides of the exposed portion of the
abrupt MIT semiconductor material layer 130. Next, the mask layer
pattern is removed.
[0087] FIG. 3 is a 2-terminal network circuit diagram including a
2-terminal semiconductor device that uses an abrupt MIT
semiconductor material according to the present invention.
[0088] Referring to FIG. 3, one electrode of a 2-terminal
semiconductor device 100 or 200 that uses the abrupt MIT
semiconductor material having either a stacking structure or a
plane structure, such as the first electrode layer 141 or 241, is
connected to a first terminal 310 and the other electrode, such as
the second electrode layer 142 or 242, is connected to a second
terminal 320 by interposing a resistance unit 300. The resistance
unit 300 has a resistance value R large enough to prevent the
failure of the 2-terminal semiconductor device 100 or 200 due to a
high current. Connecting it to a transistor or a power source uses
the 2-terminal network circuit.
[0089] FIG. 4 is a graph showing an effect of hole doping in the
abrupt MIT semiconductor material of FIGS. 1 and 2. The inner curve
of the graph is given by equation m*/m=1/(1-.rho..sup.4), where m*
is effective mass and .rho. is band filling factor of a carrier in
a metal. Electric conductivity .sigma. is proportional to
(m*/m).sup.2. The relationship-type of the factors is disclosed in
the article "New Trends in Superconductivity" by Hyun-Tak Kim
published in NATO Science Series Vol II/67 (Kluwer, 2002) pp. 137
and at the web address
http://xxx.lanl.gov/abs/cond-mat/0110112.
[0090] Referring to FIG. 4, in the case of a Mott-Brinkman-Rice
insulator (Mott insulator) which is not a metal although the number
of electrons is equal to the number of the atoms, the
Mott-Brinkman-Rice insulator transition to a metal from an
insulator when a band filling factor .rho., which is a ratio of the
number of atoms to the number of electrons, is less than 1, that
is, a hole doping occurs. The reduction of the band filling factor
.rho. in a Mott-Brinkman-Rice insulator from 1 to less than 1
denotes that a hole doping has occurred. In FIG. 4, a dotted line
indicated by reference number 410 denotes an insulator that rapidly
jumps to a metal and a line indicated by reference number 420
denotes the effective mass m*/m of electrons in a metal state after
transitioning to the metal. It is well known that electric
conductivity is proportional to the square of the effective mass
m*/m of the electrons in a metal state. Accordingly, if a very low
concentration of holes is doped to the Mott-Brinkman-Rice
insulator, the insulator transitions to a metal. In this case, as
the amount of holes that generate the hole doping increases, the
degree of jumping is decreased and a low electric conductivity is
implemented. On the contrary, as the amount of holes added is
decreased, the degree of jumping increases and a high electric
conductivity is implemented. Conventionally, a semiconductor has
been interpreted not as a Mott-Brinkman-Rice insulator. However,
considering the characteristics of the Mott-Brinkman-Rice insulator
disclosed in the aforementioned theory wherein a semiconductor
material also has an energy gap less than 2 eV and a hole level or
an electronic level, a 2-terminal semiconductor device can be
manufactured.
[0091] FIG. 5 is a graph showing the existence of a sub-gap less
than 2 eV in the abrupt MIT semiconductor material of FIGS. 1 and
2. This is photoemission spectroscopy data disclosed by R.
Zimmermann, R. Claessed, F. Reinert, P. Steiner, S. Hufner, in J.
Phys.: Condens. Matter 10 (1998) 5697.
[0092] Referring to FIG. 5, the existence of sub-gaps (refer to
reference number 521 and 531) having a binding energy less than 2
eV except the main gaps having a binding energy (or an energy gap)
of approximately 6 eV is seen in photoemission spectrums of
VO.sub.2 (refer to reference number 520) and V.sub.2O.sub.3 (refer
to reference number 530), which are Mott-Brinkman-Rice insulators
that show a rapid transition to metals according to hole doping as
described with reference to FIG. 4. However, the photoemission
spectrum (refer to reference number 510) of V.sub.2O.sub.5 that
does not generate an abrupt MIT by the hole doping shows only a
main gap but no sub-gap is observed at a binding energy level less
than 2 eV. This result indicates that a material that generates an
abrupt MIT has a sub-gap at a binding energy less than 2 eV. This
is an aspect of the Mott-Brinkman-Rice insulator and also an aspect
of a semiconductor.
[0093] FIG. 6 is a graph showing the result of a hall effect for
explaining the change of carriers according to temperature in the
abrupt MIT semiconductor material of FIGS. 1 and 2.
[0094] Referring to FIG. 6, the hole concentration ranges
approximately
1.25.times.10.sup.15/cm.sup.3-7.37.times.10.sup.15/cm.sup.3 at a
temperature below 332 K (refer to FIG. 6A). The symbol "-" in FIG.
6 indicates holes. The holes showing the concentration in the range
of 1.25.times.10.sup.15/cm.sup.3-7.37.times.10.sup.15/cm.sup.3
exist in the valence band. However, in fact, a small amount of
unmeasured exists in the hole level besides the hole in the valence
band. The holes in the hole level appear as the temperature
increases and approximately 1.16.times.10.sup.17/cm.sup.3 of the
holes are measured when the temperature increases to approximately
332 K (refer to FIG. 6B). If the temperature further increases, a
number of electrons are measured, and the number of electrons
drastically increases as the temperature further increases (refer
to FIG. 6C). Consequently, when the temperature of the
Mott-Brinkman-Rice insulator increases, holes in the hole level are
measured at a temperature of approximately 332 K, and if the
temperature further increases, the Mott-Brinkman-Rice insulator
rapidly transitions to a metal. The temperature dependence of the
hole is also an aspect of a semiconductor.
[0095] FIG. 7 is a graph showing the change of resistance according
to temperature in the abrupt MIT semiconductor material of FIGS. 1
and 2.
[0096] Referring to FIG. 7, resistances according to temperature
changes are measured after forming a VO.sub.2 layer, which is a
Mott-Brinkman-Rice insulator, on a sapphire (Al.sub.2O.sub.3)
(crystal face is 1102) substrate. The results show that the
VO.sub.2 layer remains in a semiconductor state (refer to 7A in
FIG. 7) that has relatively high resistance values at temperatures
below 332 K, generates a rapid transition to a metal at a
temperature of approximately 332 K, and reaches a metal state
(refer to 7B in FIG. 7) that has relatively low resistance values
at temperatures greater than approximately 340 K. This result is
identical to the result described with reference to FIG. 6 in that
the semiconductor rapidly transitions to a metal as the result of
hole doping according to temperature change. The exponential
reduction of resistance according to the temperature increase in
region 7A is an aspect of a semiconductor.
[0097] FIG. 8 is a graph showing the test results of Raman
scattering for observing the structural change of a material
according to a temperature change. In FIG. 8, x-axis and y-axis
respectively represents a Raman shift and the intensity of
spectrum.
[0098] Referring to FIG. 8, when the temperature of a structural
phase transition changes from a low temperature to a high
temperature, that is, from 45.degree. C. to 85.degree. C., the
location of an atom also changes. More specifically, as a dotted
line indicated by the reference number 800, an A.sub.g peak of the
largest monoclinic structure at 622 cm.sup.-1 at a temperature of
45.degree. C. is changed to an A.sub.1g peak of a wide tetragonal
structure at 570 cm.sup.-1 at temperature of 85.degree. C.
Therefore, it can be seen that the location of an atom can vary
according to the change of peak location that represents the
polarization of an atom at a particular location. The location
change of an atom means that a structural phase transition was
generated, and accordingly, a structural phase transition can be
generated by the temperature change.
[0099] FIG. 9 is a graph showing the results of spectroscopic micro
Raman scattering tests in an abrupt MIT semiconductor with respect
to VO.sub.2, which is an abrupt MIT semiconductor material of FIGS.
1 and 2, for observing the structural change of a material
according to current change.
[0100] Referring to (a) in FIG. 9, in the case of the VO.sub.2
layer on a sapphire (Al.sub.2O.sub.3) substrate (crystal face is
1102), when observing the location change of a peak indicated as
reference number 900, the A.sub.g peak of the monoclinic at 622
cm.sup.-1 is not changed until the current flow in the VO.sub.2
layer reaches 18 mA and disappears above 18 mA. This indicates that
the structural phase transition is not generated below 20 mA. Peaks
that exist above 16 mA are the peaks of Al.sub.2O.sub.3 of the
substrate. The location change of atoms, which indicates the
generation of a structural phase transition, occurs and the
A.sub.1g peak, which indicates a wide tetragonal structure, appears
above the current flow of approximately 30 mA. This means that the
structural phase transition is generated above 30 mA. However, it
will be described with reference to FIG. 11 later on, the fact that
the current flow in the VO.sub.2 layer is approximately 5 mA means
that a rapid transition to a metal has been generated by hole
doping in the VO.sub.2 layer. This proves that the structural phase
transition by a rapid transition to a metal by hole doping is not
generated. The structural phase transition when a current flows
greater than approximately 30 mA is a phenomenon that takes place
by heat generated by a current that flows in the VO.sub.2 layer and
is not directly related to the rapid transition to a metal by hole
doping. Consequentially, the rapid transition to a metal by hole
doping is different from the structural phase transition. This
structural phase transition is a secondary phenomenon.
[0101] Referring to portion (b) in FIG. 9, when the current flow in
the VO.sub.2 layer is approximately 100 mA, the measurement of the
location change of atoms is difficult because the Raman shift peaks
are screened by a lot of currents. This proves that the VO.sub.2
layer has a metal characteristic.
[0102] FIG. 10 is a graph showing the characteristic of
voltage-current of the abrupt MIT semiconductor material of FIGS. 1
and 2 according to temperature change. The x-axis in FIG. 10
represents a drain-source voltage V.sub.DS applied to both ends of
the VO.sub.2 layer on a sapphire (Al.sub.2O.sub.3) substrate
(crystal face is 1102) and the y-axis represents a current I.sub.DS
and current density J.sub.DS that flows on both ends of the
VO.sub.2 layer. The length of the both ends of the VO.sub.2 layer,
that is, the channel length is 5 .mu.m.
[0103] Referring to FIG. 10, a rapid transition to a metal takes
place at a temperature lower than the temperature of approximately
338 K at which the structural phase transition generates at a
drain-source voltage V.sub.DS. As the temperature increases, the
drain-source voltage V.sub.DS, at which a rapid transition to a
metal takes place, is decreased. At a higher temperature than 338 K
(65.degree. C.), that is, when the structural phase transition has
already occurred by a temperature change, the abrupt MIT
semiconductor material satisfies the ohm's law. Consequentially,
the rapid transition to a metal takes place at a lower temperature
than a temperature at which the structural phase transition
generates. Therefore, there is no direct relation between the
structural phase transition and the rapid transition to a metal.
The structural phase transition takes place due to the temperature
increase of the device by an excessive current after the
metal-insulator transition. This denotes that the metal-insulator
transition indirectly affects the structural phase transition.
[0104] FIG. 11 is a graph showing a voltage-current characteristic
in the 2-terminal network circuit of FIG. 3. In FIG. 11, the
semiconductor device of a plane structure of FIG. 2 is used as the
2-terminal semiconductor device that uses an abrupt MIT
semiconductor material. More specifically, a sapphire
(Al.sub.2O.sub.3) layer is used as the substrate, the VO.sub.2
layer is used as the abrupt MIT semiconductor material, a two layer
of Au/Cr is used as the first and second electrodes, and the
channel length of the VO.sub.2 layer between the first and the
second electrodes is 5 .mu.m. The resistance unit has a resistance
value of 1 k.OMEGA..
[0105] Referring to FIG. 11, the VO.sub.2 layer maintains an
insulating state (refer to 11A) until the drain-source voltage
V.sub.DS of approximately 22.5 V applied between the first
electrode and the second electrode, but at a higher voltage than
22.5 V, the VO.sub.2 layer becomes a metal state (refer to 11B) by
a rapid transition to a metal. This means that if a voltage of
approximately 22.5 V is applied, that is, a field greater than a
predetermined magnitude is applied to both ends of the VO.sub.2
layer, and than an abrupt MIT is generated by hole doping. When the
VO.sub.2 layer is in a metal state (11B) from an insulating state
(11A) by generating an abrupt MIT by hole doping, a current flows
in the VO.sub.2 layer and the magnitude of the current is greater
than approximately 15 mA.
[0106] FIG. 12 is a graph showing the hysteresis characteristic of
a metal state of the abrupt MIT semiconductor material of FIGS. 1
and 2.
[0107] Referring to FIG. 12, from the measurement results of the
current density change according to the variation of field E.sub.DS
applied to both ends of the abrupt MIT semiconductor material, it
is seen that there is a hysteresis characteristic in a metal state
as the result of an abrupt MIT, that is, a characteristic of
changing current density J.sub.DS sequentially as indicated by the
arrows 12A.fwdarw.12B.fwdarw.12C.fwdarw.12D. This proves that hole
doping causes an abrupt MIT when applying a field.
[0108] FIG. 13 is a graph showing the voltage-current
characteristic in a 2-terminal semiconductor device using a
VO.sub.2 layer as an abrupt MIT semiconductor material.
[0109] Referring to FIG. 13, in a semiconductor device that uses an
abrupt MIT semiconductor material having a stacking structure of
FIG. 1, if the VO.sub.2 layer is used as the abrupt MIT
semiconductor material, it is seen that the VO.sub.2 layer has
changed from an insulator state (13A) to a metal state (13B) by an
abrupt MIT by hole doping as the result of applying a predetermined
voltage to both ends of the VO.sub.2 layer.
[0110] FIG. 14 is a graph showing the voltage-current
characteristic in a 2-terminal semiconductor device that uses
p-type gallium arsenic (GaAs) as an abrupt MIT semiconductor
material.
[0111] Referring to FIG. 14, as the result of applying a
predetermined voltage V.sub.DS to both ends of a p-type GaAs layer
after forming the p-type GaAs layer on a GaAs substrate, the GaAs
layer has changed to a metal state (14B) from an insulator state
(14A) by the generation of abrupt MIT by hole doping. Here, the
p-type GaAs is a material having a sub-band less than 2 eV and
holes in the hole level, and it is seen that the rapid transition
to a metal has been generated by hole doping when applying a
voltage of approximately 30 V. The low concentration hole when the
abrupt MIT is generated is n 0.001% 1.times.10.sup.14 cm.sup.-3
from n.apprxeq.(0.2/a.sub.H).sup.3.
[0112] FIG. 15 is a graph showing the voltage-current
characteristic in a 2-terminal semiconductor device that uses
p-type GaAs as an abrupt MIT semiconductor material.
[0113] Referring to FIG. 15, in the case of forming an aluminum
arsenic (AlAs) buffer layer between the GaAs substrate and the
p-type GaAs layer, when applying a relatively high voltage
comparing to the case without the AlAs buffer layer, it is seen
that the insulator state (14A) has changed to a metal state (14B)
by generating an abrupt MIT. However, the voltage difference is
minute.
[0114] FIG. 16 is a graph showing the voltage-current
characteristic according to temperature change in a 2-terminal
semiconductor device that uses p-type GaAs as an abrupt MIT
semiconductor material. Here, the channel length of the p-type GaAs
is approximately 10 .mu.m.
[0115] Referring to FIG. 16, in the case of forming a p-type GaAs
layer on the GaAs substrate, the rapid transition of the p-type
GaAs layer to a metal state (16B1) from an insulator state (16A1)
is generated at a voltage of approximately 80 V and at a
temperature of 300K which is relatively the lowest temperature. At
a relatively high temperature of 330K, the abrupt MIT in the p-type
GaAs layer from an insulator state (16A2) to a metal state (16B2)
is generated at a voltage of approximately 55V. At a relatively
high temperature of 350K, the p-type GaAs layer changes from an
insulator state (16A3) to a metal state (16B3) at a voltage of
approximately 53 V. These results show a relation between a voltage
applied for generating an abrupt MIT and temperature, and indicate
that, consequentially, as the temperature increases, the applied
voltage for generating an abrupt MIT is low, and there is no
difference of voltages applied for generating an abrupt MIT above a
certain temperature level.
[0116] FIG. 17 is graph showing the characteristic of hysteresis of
a metal phase of p-type GaAs as an abrupt MIT semiconductor
material. Here, the channel length of the p-type GaAs is
approximately 10 .mu.m.
[0117] Referring to FIG. 17, the measurement results of current
density J.sub.DS according to the variation of voltage V.sub.DS
applied to both ends of an abrupt MIT semiconductor material show a
hysteresis characteristic in a metal state as a result of
generating an abrupt MIT, that is, the change of current density
J.sub.DS sequentially as indicated by the arrows
(17A.fwdarw.17B.fwdarw.17C.fwdarw.17D). This result proves that the
abrupt MIT can be generated in the p-type GaAs by hole doping by
applying a field.
[0118] FIG. 18 (a) is a graph showing the temperature dependence of
electric conductivity of GaAs. These data are disclosed by G.
Gattow and G. Buss and published in Naturwissenschaften 56 (1)
(1969) 35. These data are quoted to show the temperature of
structural phase transition of GaAs. FIG. 18(b) is a graph showing
the temperature dependence of resistance of p-type GaAs to which a
low concentration of holes is added. Resistance is inverse
proportional to electric conductivity.
[0119] More specifically, FIG. 18(a) shows a line of rapid
discontinuity of electric conductivity at temperature of
approximately 1240.degree. C. This result indicates that a
structural phase transition from a monoclinic to a tetragonal
structure is generated at a temperature below 1240.degree. C. FIG.
18(b) shows the resistance of p-type GaAs, to which a low hole
concentration of 5.times.10.sup.14 cm.sup.-3 is added, measured to
temperature of 480K, and shows no abrupt MIT. Therefore, since the
abrupt MIT observed in FIGS. 14, 15, 17, and at temperatures of
300K, 330K, and 350K in FIG. 16 are generated at a far lower
temperature than the temperature of the structural phase
transition, it can be said that the abrupt MIT observed in GaAs is
not directly related to the structural phase transition.
[0120] FIG. 19 is a graph showing the characteristic of
photocurrent measured using an Ar ion laser of 514.5 nm in a
2-terminal semiconductor device that uses p-type GaAs as an abrupt
MIT material. Here, the channel length of the p-type GaAs is
approximately 10 .mu.m.
[0121] Referring to FIG. 19, the characteristic of photocurrent is
defined by a difference between a measured current-voltage
characteristic (19A2) while irradiating a laser and a measured
current-voltage characteristic (19A1) without irradiating a laser.
The characteristic of photocurrent is shown as a curved line
"19A3." The curved lines "19A2" and the "19A3" overlap-type below
the voltage of 27.5 V at which an abrupt MIT is generated in the
curved line "19A1." This is because the difference of the curved
lines between the "19A2" and the "19A1" is equal to the curved line
"19A2" since the value of the curved line "19A1" is so small. This
means that the magnitude of curved line "19A3" is almost identical
to the photocurrent generated by hole carriers (photocurrent
carrier) excited by a laser when irradiating the laser to p-type
GaAs. Accordingly, the 2-terminal device of the present invention
can be used as a photo sensor using the large photocurrent. A
conventional photo sensor has a stack of tens of thin layer layers
to increase the photocurrent effect. However, the use of the
2-terminal device of the present invention can simplify the
structure. Moreover, when a radio frequency (RF) emitter is used
instead of laser, the 2-terminal device like a photoelectric sensor
can be used as a RF receiver. On the other hand, the reducing
photocurrent characteristic above 27.5 V indicated by a curved line
"19A3" is because the photoconductive characteristic is not
generated in a metal. This is an aspect of an abrupt MIT.
[0122] FIG. 20 is a graph of spectrums showing the intensity and
wave dependence of photo-luminescence (PL) emitted from the
2-terminal semiconductor device of FIG. 2 manufactured that uses
p-type GaAs as an abrupt MIT material and a buffer layer formed of
AlAs by irradiating an Ar laser having a wave length of 488 nm.
[0123] Referring to FIG. 20, a graph indicated by a slim line
represents a spectrum measured at 0V of electric field applied to
the first and second electrodes, and a graph indicated by a thick
line represents a spectrum measured at 34 V of electric field
applied to the first and second electrodes. An abrupt MIT has been
generated in the vicinity of 34V. The peak "20A1" corresponds to
the sub-energy gap of GaAs having approximately 1.45 eV at a
wavelength of 860 nm. This proves that the p-type GaAs is a
semiconductor having an energy gap of less than 2 eV, to which
holes are added. The intensity of sub-energy PL was rapidly reduced
when a voltage of 34 V is applied between the first and second
electrodes. However, the peak "20A2" indicates that a certain peak
remains due to the existence of a material that does not generate
an abrupt MIT. This is because that the p-type GaAs is mixed with a
material that generates an abrupt MIT and a material that does not
generate an abrupt MIT. The intensity of spectrum has increased
consecutively from 800 nm to 600 nm after generating an abrupt MIT
by applying an electric field. The sudden reduction of the spectrum
curve toward short wavelengths from 600 nm is because the short
wavelengths are removed using a filter. The increase in the
intensity ("20A4") of PL from the wavelength of 800 nm to 600 nm is
understood as a result of emitting light from the 2-terminal
device. Light having a wavelength in the vicinity of 640 nm
corresponds to red light. Therefore, the 2-terminal device of FIG.
2 can be used as a light-emitting device, such as a light emitting
diode (LED) or a laser.
[0124] The phenomenon of consecutively increasing the intensity of
PL from the wavelength of 800 nm to 600 nm is interpreted as a
light emission by Bremsstrahlung radiation wherein electrons
produced by the abrupt MIT generate electromagnetic waves of
consecutive spectrum by accelerating the electrons in a strong
electric field (E=V/d.sub.channel length=34 V/5
.mu.m=6.8.times.10.sup.6 V/m). This is the same principle of an
accelerator that generates a certain kind of light. The 2-terminal
device can be considered as a super mini-accelerator having an
acceleration length of 5 .mu.m.
[0125] FIG. 21 is a graph showing a current-voltage characteristic
measured by a current control method that measures voltage with a
current flow of 10 .mu.A in a 2-terminal device that uses p-type
GaAs as an abrupt MIT material. Here, the channel length of p-type
GaAs is approximately 10 .mu.m.
[0126] Referring to FIG. 21, when a current of 10 .mu.A is applied
for the first time, a voltage of 55 V (21A) is measured. Next, when
the current is increased by 10 .mu.A for each time, the voltage
decreases discontinuously to approximately 25 V (21B). When the
current is further increased, the voltage increases by the Ohm's
law. The discontinuous reduction of measured voltages from 55V
(21A) to 25V (21B) corresponds to an abrupt MIT because a straight
line "21C", which shows the Ohm's law, indicates a metal
characteristic. The phenomenon of decreasing and increasing voltage
according to the increase of current is called a negative
resistance or a negative differential resistance. The detection of
a negative characteristic in a semiconductor to which a low
concentration of hole, such as p-type GaAs, is injected is an
aspect of a phase change memory. This means that p-type GaAs can be
used as a material for forming a nonvolatile memory. Also, all
semiconductor materials to which a low concentration of hole is
added may show a negative resistance characteristic.
[0127] FIG. 22 is a perspective view illustrating a shape of an
electrode of the 2-terminal semiconductor device in FIG. 2.
[0128] Referring to FIG. 22, if the first and the second electrodes
241 and 242 have a plane structure facing each other on an abrupt
MIT semiconductor material layer 300, the length of surface facing
each other can be increased by forming the first and second
electrodes 241 and 242 in a finger shape, thereby the amount of
current flow per unit area increases. In the drawing, even though
the first electrode 241 is formed to have three fingers and the
second electrode 242 is formed to have two fingers, the number of
fingers can be increased. Also, the length of fingers and the
horizontal distance L between the first electrode 241 and the
second electrode 242 can be controlled as desired.
[0129] FIGS. 23A and 23B are respectively a perspective view of an
abrupt MIT semiconductor material layer and a graph for explaining
a relationship-type of length and width according to the variation
of thickness of the abrupt MIT semiconductor material of FIGS. 1
and 2.
[0130] Referring to FIGS. 23A and 23B, a width W, a length L, a
thickness t, and an area A of an abrupt MIT semiconductor material
layer 130 or 230 must be harmonized from each other. That is, when
a metal-insulator transition is generated at room temperature, in
order to be able to have the resistance change approximately
10.sup.4.OMEGA. before and after generating the transition, if the
thickness of the thin layer is 100 nm, the length L is
approximately 20 .mu.m and the width W is approximately 3 mm as
indicated by dotted lines in FIG. 23(B). Controlling the thickness
t, the length L, and the width W can properly maintain a desired
resistance change.
[0131] As described above, according to the 2-terminal
semiconductor device that uses an abrupt MIT semiconductor material
according to the present invention and the method of manufacturing
the same, a device that can obtain a high current from a small area
and can operate at a high speed can be manufactured by using the
abrupt MIT semiconductor material by hole doping not by using a
structural phase transition. The device can be applied to a variety
of fields including a warning device, a temperature sensor, a
switching device, a memory device, a cell protection circuit, a
phase change memory, a magnetic memory which uses an abrupt MIT and
a ferromagnetic thin layer, a photoelectric sensor, a high speed
optical communication receiver, an RF detector, or a transistor,
which requires a large current at an arbitrary temperature.
[0132] While the present invention has been particularly shown and
described with reference to exemplary embodiments thereof, it will
be understood by those of ordinary skill in the art that various
changes in form and details may be made therein without departing
from the spirit and scope of the present invention as defined by
the following claims.
* * * * *
References