U.S. patent application number 17/064250 was filed with the patent office on 2022-04-21 for light emitting diode device.
The applicant listed for this patent is XIAMEN SANAN OPTOELECTRONICS TECHNOLOGY CO., LTD.. Invention is credited to Chia-hung CHANG, Anhe HE, Ling-yuan HONG, Su-hui LIN, Xiaoliang LIU, Kang-wei PENG.
Application Number | 20220123176 17/064250 |
Document ID | / |
Family ID | 1000006253110 |
Filed Date | 2022-04-21 |
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United States Patent
Application |
20220123176 |
Kind Code |
A2 |
LIU; Xiaoliang ; et
al. |
April 21, 2022 |
LIGHT EMITTING DIODE DEVICE
Abstract
An LED device includes an epitaxial layered structure, a current
spreading layer, a first insulating layer and a reflective
structure. The current spreading layer is formed on a surface of
the epitaxial layered structure. The first insulating layer is
formed over the current spreading layer, and is formed with at
least one first through hole to expose the current spreading layer.
The reflective structure is formed on the first insulating layer,
extends into the first through hole, and contacts with the current
spreading layer. The current spreading layer is formed with at
least one opening structure to expose the surface of the epitaxial
layered structure.
Inventors: |
LIU; Xiaoliang; (Xiamen,
CN) ; HE; Anhe; (Xiamen, CN) ; PENG;
Kang-wei; (Xiamen, CN) ; LIN; Su-hui; (Xiamen,
CN) ; HONG; Ling-yuan; (Xiamen, CN) ; CHANG;
Chia-hung; (Xiamen, CN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
XIAMEN SANAN OPTOELECTRONICS TECHNOLOGY CO., LTD. |
Xiamen |
|
CN |
|
|
Prior
Publication: |
|
Document Identifier |
Publication Date |
|
US 20210066549 A1 |
March 4, 2021 |
|
|
Family ID: |
1000006253110 |
Appl. No.: |
17/064250 |
Filed: |
October 6, 2020 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
PCT/CN2018/082195 |
Apr 8, 2018 |
|
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17064250 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01L 2933/0025 20130101;
H01L 33/46 20130101; H01L 33/405 20130101; H01L 2933/0016 20130101;
H01L 33/382 20130101 |
International
Class: |
H01L 33/40 20060101
H01L033/40; H01L 33/46 20060101 H01L033/46; H01L 33/38 20060101
H01L033/38 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 1, 2020 |
CN |
20201025778.3 |
Claims
1. A light emitting diode (LED) device, comprising: an epitaxial
layered structure including a first-type semiconductor layer, an
active layer and a second-type semiconductor layer sequentially
disposed in such order; a current spreading layer formed on a
surface of said second-type semiconductor layer opposite to said
active layer; a first insulating layer formed over said current
spreading layer and formed with at least one first through hole to
expose a portion of said current spreading layer; and a reflective
structure formed on said first insulating layer, extending into
said at least one first through hole, and contacting with said
current spreading layer, wherein said current spreading layer is
formed with at least one opening structure to expose a portion of
said surface of said second-type semiconductor layer opposite to
said active layer, and said opening structure is arranged in a
staggered arrangement with said first through hole.
2. The LED device of claim 1, wherein said first insulating layer
is further formed on said surface of said second-type semiconductor
layer, and is further formed with at least one second through hole
to expose a portion of said surface of said second-type
semiconductor layer, said reflective structure extending into said
second through hole, and contacting with said surface of said
second-type semiconductor layer.
3. The LED device of claim 2, wherein said first insulating layer
is formed with a plurality of said first through holes that are
arranged in an array.
4. The LED device of claim 3, wherein said first insulating layer
is further formed with a plurality of second through holes, each of
which is formed in one of a continuous loop shape, a discontinuous
loop shape and a strip shape.
5. The LED device of claim 4, wherein a ratio of the number of said
first through holes to the number of said second through holes
ranges from 5:1 to 50:1.
6. The LED device of claim 3, wherein said first through holes have
a total cross-sectional area accounting for 3% to 50% of an area of
a projection of said epitaxial layered structure on said
substrate.
7. The LED device of claim 1, wherein said opening structure
includes at least one first opening to expose a portion of said
surface of said second-type semiconductor layer, said first
insulating layer extending into said first opening and contacting
with said second-type semiconductor layer.
8. The LED device of claim 7, wherein said first insulating layer
is formed with a plurality of said first through holes that are
spaced apart from each other, and said current spreading layer is
formed with a plurality of said first openings.
9. The LED device of claim 8, wherein said first insulating layer
is further formed on said surface of said second-type semiconductor
layer and is further formed with a plurality of second through
holes to expose a portion of said second-type semiconductor layer,
said second through holes being spaced apart from said first
through holes and said first openings, said reflective structure
extending into said second through holes and contacting with said
second-type semiconductor layer.
10. The LED device of claim 8, wherein each of said first through
holes is surrounded by said first openings of said current
spreading layer, said first openings immediately adjacent to said
first through hole being arranged in a polygon pattern.
11. The LED device of claim 8, wherein each of said first openings
of said current spreading layer has a diameter ranging from 2 .mu.m
to 50 .mu.m.
12. The LED device of claim 8, wherein said first openings of said
current spreading layer are spaced apart from each other by a
spacing ranging from 1 .mu.m to 20 .mu.m.
13. The LED device of claim 8, wherein said first openings have a
total cross-sectional area accounting for 5% to 50% of an area of a
projection of said epitaxial layered structure on said
substrate.
14. The LED device of claim 8, wherein said first openings of said
current spreading layer are arranged in an array. 20
15. The LED device of claim 8, wherein a ratio of the number of
said first openings to the number of said first through holes
ranges from 2:1 to 20:1.
16. The LED device of claim 8, wherein said first openings and said
first through holes are cooperatively arranged in an array.
17. The LED device of claim 8, wherein said first through holes of
said first insulating layer have a total cross-sectional area
accounting for 3% to 50% of an area of a projection of said
epitaxial layered structure on said substrate.
18. The LED device of claim 9, wherein a ratio of the number of
said first through holes and the number of said second through
holes ranges from 5:1 to 50:1.
19. The LED device of claim 9, wherein said first openings of said
current spreading layer and said first through holes of said first
insulating layer are arranged in an array, and each of said second
through holes is formed in one of a continuous loop shape, a
discontinuous shape and a strip shape.
20. The LED device of claim 1, wherein said first insulating layer
is made of a material selected from the group consisting of silicon
nitride, silicon oxide, aluminum oxide, magnesium fluoride,
titanium dioxide, and combinations thereof.
21. The LED device of claim 1, wherein said current spreading layer
has a thickness ranging from 5 nm to 60 nm.
22. The LED device of claim 1, wherein said active layer is
configured to emit light having an emission wavelength not greater
than 520 nm.
23. The LED device of claim 2, wherein said epitaxial layered
structure is formed with at least one recess that extends through
said second-type semiconductor layer and said active layer, and
that terminates at said first-type semiconductor layer to expose
said first-type semiconductor layer.
24. The LED device of claim 23, wherein said second through hole is
formed in one of a continuous loop shape and a discontinuous loop
shape, corresponds in position to and surrounds said at least one
recess, said second through hole having a diameter larger than that
of said at least one recess.
25. The LED device of claim 24, wherein said recess is defined by a
recess-defining wall, said first insulating layer covering said
recess-defining wall and exposing said first-type semiconductor
layer.
26. The LED device of claim 25, further comprising a first
electrode which is electrically connected to said first-type
semiconductor layer through said recess, and a second electrode
which is disposed on said reflective structure and which is
electrically connected to said second-type semiconductor layer.
27. The LED device of claim 26, further comprising a second
insulating layer that is disposed over said reflective structure,
that is formed with a first penetrating hole which is spatially
communicated with said recess to expose said first-type
semiconductor layer, and that is formed with a second penetrating
hole to expose said reflective structure, said second electrode
being disposed on said second insulating layer and filling said
second penetrating hole to contact with said reflective structure,
said first electrode being disposed on said second insulating layer
and being electrically connected to said first-type semiconductor
layer through said recess and said first penetrating hole.
28. The LED device of claim 27, wherein said second insulating
layer further covers said recess-defining wall, and is made of an
insulating reflective material.
29. The LED device of claim 1, wherein said first insulating layer
includes a distributed Bragg reflector.
30. The LED device of claim 1, wherein said reflective structure
includes a metallic reflecting layer and a metallic barrier layer
sequentially formed on said first insulating layer in such
order.
31. The LED device of claim 1, wherein said first insulating layer
has a thickness larger than a thickness of said current spreading
layer.
32. The LED device of claim 7, wherein: said LED device further
comprises an extended electrode disposed on said current spreading
layer and electrically contacted with said second-type
semiconductor layer through said first opening; and said first
insulating layer and said reflective structure are integrally
formed as a reflective insulating member which is disposed over
said extended electrode and said current spreading layer, and which
has a first penetrating hole to expose said first-type
semiconductor layer and a second penetrating hole to expose said
extended electrode.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application is a continuation-in-part (CIP) of
International Application No. PCT/CN2018/082195, filed on Apr. 8,
2018. This application also claims priority of Chinese Invention
Patent Application No. 202010252278.3, filed on Apr. 1, 2020. The
entire content of each of the international and Chinese patent
applications is incorporated herein by reference.
FIELD
[0002] The disclosure relates to a semiconductor electronic device,
and more particularly to a light emitting diode device.
BACKGROUND
[0003] Illuminating devices, i.e., light emitting diode (LED)
devices, are generally used as solid light sources which have
advantages of long lifespan, energy conservation, recyclability and
safety. LED devices are usually made of a semiconductor material,
such as gallium nitride (GaN), gallium arsenide (GaAs), gallium
phosphide (GaP) and gallium arsenide phosphide (GaAsP).
[0004] A conventional LED device includes a light emitting
epitaxial layered structure, and a reflective layer disposed on the
light emitting epitaxial layered structure. Such reflective layer
might be a distributed Bragg reflector (DBR) having a relatively
larger refractive index difference or might be a metal layer (such
as Ag layer) having a relatively higher reflectance. However, the
DBR exhibits angular dependence and unsatisfactory thermal
conductivity, and the reflectance of the metal layer which is
generally approximately 95%, is difficult to be increased.
Therefore, the external light extraction of the conventional LED
device might be adversely affected by these reflective layers,
thereby confining the illumination efficiency of the conventional
LED device.
[0005] In addition, since the LED device having a flip chip
structure is free of wire bonding and has high luminous efficacy
and good heat dissipation, such flip chip LED device are widely
developed for various applications. The flip chip LED device often
utilizes a transparent conductive layer (e.g., electrically
conductive metal oxide such as ITO) as a P-type ohmic contact layer
for an epitaxial layered structure. Nevertheless, the transparent
conductive layer still has a predetermined optical loss after being
subjected to a melting process at high temperature for achieving a
higher transmittance. The predetermined optical loss may inhibit
the increase of brightness of the flip chip LED device. Moreover,
formation of an ohmic contact in a p-type semiconductor layer of
the flip chip LED device is difficult to be achieved without using
such transparent conductive layer.
SUMMARY
[0006] Therefore, an object of the disclosure is to provide an LED
device that can alleviate at least one of the drawbacks of the
prior art.
[0007] According to the disclosure, the LED device includes an
epitaxial layered structure, a current spreading layer, a first
insulating layer and a reflective structure. The epitaxial layered
structure includes a first-type semiconductor layer, a second-type
semiconductor layer, and an active layer disposed between the
first-type and second-type semiconductor layer. The current
spreading layer is formed on a surface of the second-type
semiconductor layer opposite to the active layer. The first
insulating layer is formed over the current spreading layer, and is
formed with at least one first through hole to expose a portion of
the current spreading layer. The reflective structure is formed on
the first insulating layer, extends into the at least one first
through hole, and contacts with the current spreading layer. The
current spreading layer is formed with at least one opening
structure to expose a portion of the surface of the second-type
semiconductor layer opposite to the active layer. The opening
structure is arranged in a staggered arrangement with the first
through hole.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] Other features and advantages of the disclosure will become
apparent in the following detailed description of the embodiments
with reference to the accompanying drawings, of which:
[0009] FIGS. 1 to 10 are fragmentary schematic views illustrating
consecutive steps of a method for manufacturing a first embodiment
of an LED device according to the disclosure, wherein FIG. 4 is a
cross sectional view taken along line A-A of FIG. 5;
[0010] FIG. 11 is a fragmentary schematic view illustrating a
second embodiment of the LED device according to the
disclosure;
[0011] FIG. 12 is a top view illustrating the second
embodiment;
[0012] FIG. 13 is a fragmentary schematic view illustrating a third
embodiment of the LED device according to the disclosure;
[0013] FIGS. 14 to 23 are fragmentary schematic views illustrating
consecutive steps of a method for manufacturing the third
embodiment, wherein FIGS. 15, 17, 19 and 21 are cross sectional
views taken along line B-B of FIGS. 14, 16, 18 and 20,
respectively;
[0014] FIG. 24 is a top view illustrating the third embodiment;
[0015] FIG. 25 is an enlarged view of FIG. 24;
[0016] FIGS. 26 and 27 are fragmentary schematic views illustrating
consecutive steps for forming a metallic reflecting layer and a
metallic barrier layer on a fourth embodiment of the LED device
according to the disclosure;
[0017] FIG. 28 is a fragmentary schematic view showing a fifth
embodiment of the LED device according to the disclosure;
[0018] FIG. 29 is a fragmentary schematic view showing a sixth
embodiment of the LED device according to the disclosure; and
[0019] FIG. 30 is a top view of the sixth embodiment.
DETAILED DESCRIPTION
[0020] Before the disclosure is described in greater detail, it
should be noted that where considered appropriate, reference
numerals or terminal portions of reference numerals have been
repeated among the figures to indicate corresponding or analogous
elements, which may optionally have similar characteristics.
[0021] Referring to FIGS. 1 to 10, a first embodiment of an LED
device 10 according to this disclosure is manufactured by a method
including the following consecutive steps.
[0022] As shown in FIG. 1, a substrate 110 is provided, and an
epitaxial layered structure 120 is formed on the substrate 110 by
e.g., a metal organic chemical vapor deposition (MOCVD)
process.
[0023] The substrate 110 may be made of, for example, planar
sapphire, patterned sapphire, silicon carbide, gallium nitride or
gallium arsenide. In this embodiment, the substrate 110 is made of
patterned sapphire. The substrate 110 may be removed or thinned
after the formation of the epitaxial layered structure 120.
[0024] The epitaxial layered structure 120 includes a first-type
semiconductor layer 121, an active layer 122 and a second-type
semiconductor layer 123 sequentially disposed on the substrate 110
in such order. The first-type semiconductor layer 121 may be one of
a P-type semiconductor layer and an N-type semiconductor layer, and
the second-type semiconductor layer 123 may be the other one of the
P-type semiconductor layer and the N-type semiconductor layer. In
this embodiment, the epitaxial layered structure 120 is a gallium
nitride (GaN)-based structure, i.e., the first-type semiconductor
layer 121 is an n-GaN layer, the second-type semiconductor layer
123 is a p-GaN layer, and the active layer 122 is a GaN-based layer
having a multiple quantum well structure. The material for making
each layer of the epitaxial layered structure 120 can be chosen
according to practical requirements, and is not limited herein.
[0025] The epitaxial layered structure 120 may further include a
buffer layer disposed between the substrate 110 and the first-type
semiconductor layer 121, and an electron blocking layer (EBL)
disposed between the active layer 122 and the second-type
semiconductor layer 123 (not shown in the figures). Referring to
FIG. 2, the epitaxial layered structure 120 is subjected to an
etching process to form at least one recess 1211 that is defined by
a recess-defining wall, that extends through the second-type
semiconductor layer 123 and the active layer 122, and that
terminates at the first-type semiconductor layer 121 to expose a
portion of the first-type semiconductor layer 121. The etching
process may be, for example, an inductively coupled plasma (ICP)
process or a reactive ion etching (RIE) process. The number of the
recess 1211 can be increased according to the structure, usage or
size of the LED device 10. It is noted that when the LED device 10
has a vertical structure, there is no need to form the recess 1211
in the epitaxial layered structure 120.
[0026] Referring to FIG. 3, a current spreading layer 130 is then
formed on a surface 123a of the second-type semiconductor layer 123
opposite to the active layer 122. The current spreading layer 130
may be made of a metal oxide that is transparent to the light
emitting from the active layer 122. Examples of the metal oxide for
making the current spreading layer 130 may include, but are not
limited to, indium tin oxide (ITO), zinc oxide (ZnO), indium zinc
tin oxide, indium zinc oxide (IZO), zinc tin oxide (ZTO), indium
gallium tin oxide, indium gallium oxide (IGO), gallium zinc oxide
(GZO), aluminum (Al)-doped zinc oxide, and fluoride-doped tin
oxide. Alternatively, the current spreading layer 130 may be made
of graphene. In this embodiment, the current spreading layer 130 is
an ITO layer made by an evaporation process or a sputtering
process. The current spreading layer 130 is capable of forming an
ohmic contact with the second-type semiconductor layer 123 by
melting. In certain embodiments, lithography and etching processes
may further be performed on the current spreading layer 130 to make
the current spreading layer 130 on the surface 123a "shrink" so
that a first insulating layer 141 to be formed subsequently can
cover the sidewall of the current spreading layer 130, as shown in
FIG. 4. Further, the current spreading layer 130 may be formed with
at least one opening structure to expose a portion of the surface
123a of the second-type semiconductor layer 123 opposite to the
active layer 122.
[0027] Referring to FIG. 4, the first insulating layer 141 is
formed over the current spreading layer 130, and is formed with at
least one first through hole 162 by etching to expose a portion of
the current spreading layer 130. The first insulating layer 141 may
further cover the recess-defining wall and expose the first-type
semiconductor layer 121. In this embodiment, the first insulating
layer 141 is formed with a plurality of the first through holes 162
arranged in an array (see FIG. 5). The opening structure of the
current spreading layer 130 is arranged in a staggered arrangement
with the first through holes 162.
[0028] The first insulating layer 141 may be formed by a chemical
vapor deposition (CVD) process, and may be made of a material
having a low refractive index, such as silicon oxide (SiO.sub.2),
magnesium fluoride (MgF.sub.2), and an aluminum oxide
(Al.sub.2O.sub.3), and/or a material having a high refractive
index, such as titanium dioxide (TiO.sub.2). In certain forms, the
first insulating layer 141 includes a distributed Bragg reflector
(DBR) made of materials having low and high refractive indices. In
other forms, the first insulating layer 141 is made of SiO.sub.2.
With the difference of refractive indices between the first
insulating layer 141 and the current spreading layer 130, an angle
of the total reflection may be changed so that the light extraction
can be enhanced. The first insulating layer 141 has a transmittance
and a thickness greater than those of the current spreading layer
130. In certain forms, the first insulating layer 141 has a
thickness greater than 50 nm.
[0029] The first through holes 162 may be formed by an etching
process. The first insulating layer 141 is further formed on the
surface 123a of the second-type semiconductor layer 123, and is
further formed with at least one second through hole 163 to expose
a portion of the surface 123a of the second-type semiconductor
layer 123. The second through hole 163 corresponds in position and
space to the opening structure of the current spreading layer 130.
The second through hole 163 also corresponds in position to and
surrounds the recess 1211. As such, the second through hole 163 has
a diameter larger than that of the recess 1211. Each of the second
through holes 163 is formed in one of a continuous loop shape (such
as a circular loop shape and a rectangular loop shape), a
discontinuous loop shape and a strip shape. In this embodiment, the
first insulating layer 141 is formed with a plurality of second
through holes 163 that are formed in continuous circular and
rectangular loop shapes (as shown in FIG. 5).
[0030] Each of the first through holes 162 and the second through
holes 163 has a diameter ranging from 1 .mu.m to 50 .mu.m. In
certain forms, the diameter of each of the first through holes 162
and the second through holes 163 ranges from 1 .mu.m to 20 .mu.m. A
ratio of the number of the first through holes 162 to the number of
the second through holes 163 ranges from 5:1 to 50:1. In certain
forms, the ratio of the number of the first through holes 162 to
the number of the second through holes 163 ranges from 10:1 to
30:1. In general, the number of the second through holes 163 is
substantially the same as the number of the recess 1211, and each
of the second through holes 163 has a shape similar to a respective
one of the recesses 1211.
[0031] The first through holes 162 of the first insulating layer
141 have a total cross-sectional area accounting for 3% to 50% of
an area of a projection of the epitaxial layered structure 120 on
the substrate 110. In certain forms, the first through holes 162
have a total cross-sectional area accounting for 5% to 20% (such as
10%) of an area of a projection of the epitaxial layered structure
120. If the total cross-sectional area of the first through holes
162 is too small, the contact area between the current spreading
layer 130 and a reflective structure 150 to be formed subsequently
thereon may be too small to allow a better control of a forward
voltage (V.sub.F). On the contrary, if the total cross-sectional
area of the first through holes 162 is too large, the reflectance
of an omni-directional reflector (ODR) structure cooperatively
formed by the current spreading layer 130, the first insulating
layer 141 (e.g., one having a low refractive index) and the
reflective structure 150 will be adversely effected.
[0032] Referring to FIGS. 6 to 8, the reflective structure 150 is
formed on the first insulating layer 141, extends into the first
through holes 162, and contacts with the current spreading layer
130. The reflective structure 150 may further extend into the
second through holes 163 and contacts with the second-type
semiconductor layer 123. In this way, the adherence between the
reflective structure 150 and the first insulating layer 141 may be
enhanced, thereby increasing the reliability of the LED device
10.
[0033] The reflective structure 150 may be formed by an evaporation
process or an sputtering process. In this embodiment, the
reflective structure 150 includes multiple layers, i.e., a metallic
reflecting layer 151 and a metallic barrier layer 152 sequentially
formed on the first insulating layer 141 in such order, but are not
limited thereto. The metallic reflecting layer 151 may be made of a
metal having high reflectance, such as aluminum (Al) or silver (Ag)
for serving as a mirror, and the metallic barrier layer 152 may be
made of titanium tungsten (TiW), chromium (Cr), platinum (Pt) or
titanium (Ti) for protecting the metallic reflecting layer 151. In
certain forms, the metallic reflecting layer 151 is fully
encapsulated by the metallic barrier layer 152.
[0034] Referring to FIGS. 9 and 10, a first electrode 171 is
electrically connected to the first-type semiconductor layer 121
through the recess 1211, and a second electrode 172 is disposed on
the reflective structure 150 and is electrically connected to the
second-type semiconductor layer 123. The first electrode 171 may be
one of an N-type electrode and a P-type electrode, and the second
electrode 172 may be the other one of the N-type electrode and the
P-type electrode. In this embodiment, the first electrode 171 is an
N-type electrode and the second electrode 172 is a P-type
electrode.
[0035] Before forming the first and second electrodes 171, 172, a
second insulating layer 142 may be first disposed over the
reflective structure 150. The second insulating layer 142 is formed
with a first penetrating hole 181 that is spatially communicated
with the recess 1211 to expose the first-type semiconductor layer
121, and is formed with a second penetrating hole 182 to expose the
reflective structure 150 (see FIG. 9). The first penetrating hole
181 serves as a window for the first electrode 171, and the second
penetrating hole 182 serves as a window for the second electrode
172. In such case, the second electrode 172 is disposed on the
second insulating layer 142, and further fills the second
penetrating hole 182 to contact with the reflective structure 150.
The first electrode 171 is disposed on the second insulating layer
142, and is electrically connected to the first-type semiconductor
layer 121 through the recess 1211 and the first penetrating hole
181.
[0036] The process and the material for making the second
insulating layer 142 may be the same as those of the first
insulating layer 141. The first and second penetrating holes 181,
182 may be formed by lithography and etching. The first penetrating
hole 181 may correspond in number to the number of the second
penetrating hole 182. The second penetrating hole 182 may have an
area equal to or larger than that of the first penetrating hole
181. Moreover, the second penetrating hole 182 may be formed in a
shape different from that of the first penetrating hole 181. For
example, the first penetrating hole 181 may be formed in a loop
shape and the second penetrating hole 182 may be formed in a strip
shape. When the first and second penetrating hole 181, 182 are
different in area and/or shape, the polarity of the first and
second electrodes 171, 172 to be disposed therein can be easily
differentiated.
[0037] The first penetrating hole 181 corresponds in number to the
number of the recess 1211. The recess 1211 may have an area larger
than that of the first penetrating hole 181, which allows the
recess-defining wall to be covered by the first and/or second
insulating layer 141, 142.
[0038] In certain forms, the first electrode 171 has an area equal
to an area of the second electrode 172. The first electrode 171 and
the second electrode 172 may be positioned in a symmetrical
relationship, such as in axial symmetry or in rotational symmetry.
An area of the first electrode 171 over the second insulating layer
142 accounts for 90% of a total area of the first electrode 171. An
area of the second electrode 172 over the second insulating layer
142 accounts for 90% of a total area of the second electrode 172.
In this way, each of the first and second electrodes 171, 172 may
have a substantially planar top surface which can be beneficial for
die bonding and packaging of the LED device 10 (e.g., a flip-chip
LED device) and thus, improves reliability thereof. In addition, an
area of the first electrode 171 above the second insulating layer
142 may be larger than an area of the first electrode 171 above the
recess 1211, so that decrease in the light emitting area caused by
the recess 1211 can be reduced while maintaining the planarity of
the first electrode 171 and eliminating the difference between the
height of the first electrode 171 to the second insulating layer
142 and the height of the first electrode to the exposed first-type
semiconductor layer 121.
[0039] Finally, the resulting LED device 10 shown in FIG. 10 may be
further cut to form separated LED chips.
[0040] It is noted that a third insulating layer (not shown) may be
further formed on the first and second electrodes 171, 172, and
then the third insulating layer may be etched to form penetrating
holes serving as windows for disposition of third and fourth
electrodes.
[0041] Referring to FIGS. 11 and 12, a second embodiment of the LED
device 10 is generally similar to the first embodiment, except that
in the second embodiment, the second through holes 163 of the first
insulating layer 141 are omitted, and the opening structure of the
current spreading layer 130 includes at least one first opening 161
to expose a portion of the surface 123a of the second-type
semiconductor layer 123. Specifically, the current spreading layer
130 is formed with a plurality of the first openings 161 that are
arranged in a staggered arrangement with the recess 1211. The first
insulating layer 141 extends into the first openings 161 and
contacts with the second-type semiconductor layer 123. In this
embodiment, the LED device 10 has a relative smaller size, e.g.,
with a length smaller than 300 .mu.m.
[0042] The current spreading layer 130 may be made of a conductive
metal oxide (such as ITO) which exhibits good current spreading
performance and is capable of forming desired ohmic contact with
the second-type semiconductor layer 123. The active layer 122 may
be configured to emit light having an emission wavelength not
greater than 520 nm. However, the conductive metal oxide may have
optical absorption at a wavelength not greater than 520 nm, and the
optical absorption becomes serious as the wavelength increases.
Taking ITO as an example, the optical absorption reaches to a range
of 3% to 15% at a wavelength ranging from around 400 nm to 460 nm,
and may be even larger at a wavelength of ultraviolet light (below
400 nm). Thus, by controlling the size and density of the first
openings 161 on the current spreading layer 130, the optical
absorption of the current spreading layer 130 may be greatly
reduced. In certain forms, the first openings 161 have a total
cross-sectional area accounting for 5% to 50% of an area of a
projection of the epitaxial layered structure 120 on the substrate
110. That is, the current spreading layer 130 may have a total area
accounting for more than 50% and less than 95% (such as 70% to 90%)
of an area of a projection of the epitaxial layered structure 120
on the substrate 110. In such way, sufficient ohmic contact between
the current spreading layer 130 and the second-type semiconductor
layer 123 can be achieved while the area of the current spreading
layer 130 can be reduced, thereby increasing the brightness of the
LED device 10.
[0043] The first openings 161 may be arranged in an array. Each of
the first openings 161 has a diameter (d1) ranging from 2 .mu.m to
50 .mu.m. The first openings 161 are spaced apart from one another
by a spacing (s1) ranging 1 .mu.m to 20 .mu.m. In this embodiment,
the diameter (d1) of each of the first openings 161 ranges from 2
.mu.m to 10 .mu.m and the spacing (s1) thereof ranges from 5 .mu.m
to 20 .mu.m.
[0044] The current spreading layer 130 may have a thickness ranging
from 5 nm to 60 nm. When the thickness of the current spreading
layer 130 is smaller than 5 nm, the forward voltage (V.sub.F) of
the LED device may increase. When the thickness of the current
spreading layer 130 is greater than 60 nm, the optical absorption
caused thereby may increase. In certain forms, the current
spreading layer 130 has a thickness ranging from 10 nm to 30 nm,
such as 15 nm or 20 nm.
[0045] The first openings 161 and the first through holes 162 are
cooperatively arranged in an array. Each of the first openings 161
has a diameter identical to that of each of the first through holes
162. A ratio of the number of the first openings 161 to the number
of the first through holes 162 ranges from 2:1 to 20:1 (such as
2:1, 3:1 or 5:1). Each of the first through holes 162 may be
surrounded by the first openings 161 of the current spreading layer
130. The first openings 161 immediately adjacent to the first
through hole 162 are arranged in a polygon pattern (D1) (see FIG.
12).
[0046] Referring to FIG. 13, a third embodiment of the LED device
10 is generally similar to the second embodiment, except that in
the third embodiment, the epitaxial layered structure 120 is formed
with a plurality of the recesses 1211. Each of the first openings
161 has a diameter ranging from 2 .mu.m to 50 .mu.m, such as 2
.mu.m to 20 .mu.m (e.g., 2 .mu.m, 5 .mu.m or 10 .mu.m). In this
embodiment, the LED device 10 has a relative larger size, e.g.,
with a length greater than 300 .mu.m. In addition, the first and
second electrodes 171, 172 and the first and second penetrating
holes 181, 182 are formed at positions different from those in the
second embodiment. Specifically, the LED device 10 further includes
a conductive metal layer 173 which is disposed on the second
insulating layer 142 and electrically connected to the first-type
semiconductor layer 121 through the recesses 1211, and a third
insulating layer 143 which is formed on the conductive metal layer
173. The first penetrating hole 181 exposes a portion of the
conductive metal layer 173. The second penetrating hole 182 extends
through the third insulating layer 143, the conductive metal layer
173 and the second insulating layer 142 to expose a portion of the
metallic barrier layer 152 of the reflective structure 150. The
third insulating layer 143 also covers sidewalls of the conductive
metal layer 173 exposed by the second penetrating hole 182. The
first and second electrodes 171, 172 are formed on the third
insulating layer 143. The first electrode 171 is electrically
contacted to the conductive metal layer 173 through the first
penetrating hole 181. The second electrode 172 is electrically
contacted to the reflective structure 150 through the second
penetrating hole 182.
[0047] The method for manufacturing the third embodiment of the LED
device 10 is described below.
[0048] Referring to FIGS. 14 and 15, the epitaxial layered
structure 120 is formed on the substrate 100 by e.g., a MOCVD
process, and then subjected to an etching process so as to obtain a
plurality of the recesses 1211.
[0049] Specifically, the epitaxial layered structure 120 includes
the first-type semiconductor layer 121, the active layer 122 and
the second-type semiconductor layer 123 sequentially disposed on
the substrate 110 in such order. In this embodiment, the first-type
semiconductor layer 121 is an n-GaN layer, the second-type
semiconductor layer 123 is a p-GaN layer, and the active layer 122
is a GaN-based layer having a multiple quantum well structure, but
are not limited thereto. The epitaxial layered structure 120 may
further include a buffer layer disposed between the substrate 110
and the first-type semiconductor layer 121, and an electron
blocking layer (EBL) disposed between the active layer 122 and the
second-type semiconductor layer 123 (not shown in the figures).
[0050] Each of the recesses 1211 is defined by a recess-defining
wall, extends through the second-type semiconductor layer 123 and
the active layer 122, and terminates at the first-type
semiconductor layer 121 to expose a portion of the first-type
semiconductor layer 121. The etching process may be, for example,
an ICP process or a RIE process.
[0051] Referring to FIGS. 16 and 17, the current spreading layer
130 is formed on the surface 123a of the second-type semiconductor
layer 123 opposite to the active layer 122, and then is patterned
by, for example, a photolithography process to form a plurality of
the first openings 161 each exposing a portion of the surface 123a
of the second-type semiconductor layer 123. The patterned current
spreading layer 130 may have a total area accounting for more than
50% and less than 95% of an area of a projection of the epitaxial
layered structure 120 on the substrate 110. Each of the first
openings 161 has a diameter ranging from 2 .mu.m to 50 .mu.m, and
the first openings 161 are spaced apart from one another by a
spacing ranging from 1 .mu.m to 20 .mu.m. In this embodiment, the
first openings 161 are arranged in an array as shown in FIG. 16,
the diameter of each of the first openings 161 ranges from 2 .mu.m
to 20 .mu.m, and the spacing of two adjacent ones of the first
openings 161 ranges from 5 .mu.m to 20 .mu.m.
[0052] Referring to FIGS. 18 and 19, the first insulating layer 141
is formed on the current spreading layer 130, is filled into the
first openings 161, and covers the recess-defining wall of each of
the recesses 1211. Then, the first insulating layer 141 is etched
to form the first through holes 162. The first through holes 162
are arranged in an array, each of which may have a diameter ranging
from 1 .mu.m to 50 .mu.m (such as 1 .mu.m to 20 .mu.m). The first
through holes 162 may have a total cross-sectional area accounting
for 3% to 50% (such as 5% to 20% or 10%) of an area of a projection
of the epitaxial layered structure 120 on the substrate 110.
[0053] Referring to FIGS. 20 and 21, the metallic reflecting layer
151 is formed on the first insulating layer 141 and contacts with
the current spreading layer 130 through the first through holes
162. Then, the metallic barrier layer 152 is further disposed over
the metallic reflecting layer 151. The metallic reflecting layer
151 may be made of a metal having high reflectance, such as
aluminum (Al) or silver (Ag) for serving as a mirror, and the
metallic barrier layer 152 may be made of titanium tungsten (TiW),
chromium (Cr), platinum (Pt) or titanium (Ti) for protecting the
metallic reflecting layer 151. The metallic reflecting layer 151
and the metallic barrier layer 152 cooperate to form the reflective
structure 150.
[0054] Referring to FIGS. 22 and 23, the second insulating layer
142 is disposed over the metallic barrier layer 152, and then the
conductive metal layer 173 is formed on the second insulating layer
142, and contacts with the exposed first-type semiconductor layer
121 through the recesses 1211. Next, the conductive metal layer 173
is subjected to an etching process to form a through hole to expose
a portion of the second insulating layer 142.
[0055] Referring back to FIG. 13, the third insulating layer 143 is
formed over the conductive metal layer 173 and contacts with the
exposed portion of the second insulating layer 142 through the
through hole. Thereafter, an etching process is performed to form
the first penetrating hole 181 which exposes a portion of the
conductive metal layer 173, and the second penetrating hole 182
which extends through the third insulating layer 143, the
conductive metal layer 173 and the second insulating layer 142 so
as to expose a portion of the metallic barrier layer 152. Finally,
the first and second electrodes 171, 172 are formed on the third
insulating layer 143 so that the first electrode 171 contacts with
the conductive metal layer 173 through the first penetrating hole
181, and the second electrode 172 contacts with the reflective
structure 150 through the second penetrating hole 182.
[0056] Referring to FIGS. 24 and 25, a fourth embodiment of the LED
device 10 is generally similar to the third embodiment, except that
in the fourth embodiment, the arrangement of the first openings 161
and the first through holes 162 is different from that of the third
embodiment. In this embodiment, one of the first through holes 162
and eight of the first openings 161 immediately adjacent to the
first through hole 162 cooperatively form a square pattern or a
rectangular pattern, and the, first through hole 162 is positioned
at a geometric center of the pattern. In this embodiment, a ratio
of the number of the first openings 161 to the number of the first
through holes 162 is approximately 3:1.
[0057] Referring to FIGS. 26 and 27, a fifth embodiment of the LED
device 10 is generally similar to the third embodiment, except that
in the fifth embodiment, the first insulating layer 141 is further
formed with a plurality of the second through holes 163, each of
which exposes a portion of the second-type semiconductor layer 123.
The second through holes 163 are spaced apart from the first
through holes 162 and the first openings 161. The shape, size and
number of the second through holes 163 may be referred to those
described in the first embodiment, and thus the details thereof are
omitted herein for the sake of brevity. The metallic reflective
layer 151 and the metallic barrier layer 152 of the reflective
structure 150 further extend into the second through holes 163 and
contact with the second-type semiconductor layer 123 of the
epitaxial layered structure 120. The sidewall of the first
insulating layer 141 also contacts with the metallic reflective
layer 151, so that the adherence between the metallic reflective
layer 151 and the first insulating layer 141 can be increased,
thereby increasing the reliability of the LED device 10.
[0058] Referring to FIG. 28, a sixth embodiment of the LED device
10 is generally similar to the second embodiment, except that in
the sixth embodiment, the reflective structure 150 only includes
the metallic reflective layer 151. The current spreading layer 130,
the first insulating layer 141 and the metallic reflective layer
151 cooperate to form an ODR structure, so as to improve the light
extraction efficiency and the brightness of the LED device 10. In
addition, the second insulating layer 142 covers the
recess-defining wall and is made of an insulating reflective
material, such as TiO.sub.2, SiO.sub.2, HfO.sub.2, ZrO.sub.2,
Nb.sub.2O.sub.5 and MgF.sub.2. When a light emitted from the active
layer 122 passes through the current spreading layer 130 and
reaches the ODR structure and the second insulating layer 142, most
of the light may be reflected back to the epitaxial layered
structure 120 by the second insulating layer 142, passes through
the substrate 110 and is then exited therefrom, so that the optical
loss caused by the light exiting from the surface and sidewall of
the epitaxial layered structure 120 may be reduced. In certain
forms, the second insulating layer 142 is capable of reflecting at
least 80% or 90% of the light emitting from the active layer 122.
The second insulating layer 142 may include a DBR, which may be
formed by alternately stacking at least two insulating dielectric
layers having different refractive indices. For example, the DBR
may include 4 pairs to 20 pairs of layers, each pair including a
TiO.sub.2 layer and a SiO.sub.2 layer, and the TiO.sub.2 layers and
the SiO.sub.2 layers in the DBR are alternately stacked. In
addition, the DBR may further include an interface layer on which
the pairs of layers are disposed, so as to improve film quality of
the DBR. The interface layer may be made of SiO.sub.2 and may have
a thickness ranging from 0.2 .mu.m to 1.0 .mu.m. Moreover, the
second insulating layer 142 covering the metallic reflecting layer
151 and sidewalls of the epitaxial layered structure 120 (i.e., the
recess-defining walls) can prevent water vapor from entering into
the epitaxial layered structure 120, thereby reducing the risk of
electrical leakage.
[0059] Referring to FIG. 29, a seventh embodiment of the LED device
10 according to the disclosure is generally similar to the second
embodiment, except for the following differences. Specifically, the
first openings 161 of the current spreading layer 130 have a total
cross-sectional area accounting for 10% to 40% of an area of a
projection of the epitaxial layered structure 120 on the substrate
110. Each of the first openings 161 of the current spreading layer
130 has a diameter ranging from 0.1 .mu.m to 50 .mu.m. The LED
device 10 may have a micro size. For example, the LED device 10 may
have a cross sectional area smaller than 62500 .mu.m.sup.2 and each
of the first openings 161 has a diameter ranging from 2 .mu.m to 10
.mu.m. Alternatively, the LED device 10 may have a medium or large
size. For example, the LED device 10 may have a cross sectional
area larger than 90000 .mu.m.sup.2 and each of the first openings
161 has a diameter equal to or larger than 2 .mu.m (such as 2 .mu.m
to 5 .mu.m, 5 .mu.m to 10 .mu.m, 10 .mu.m to 20 .mu.m, or more than
20 .mu.m). In certain forms, each of the first openings 161 has a
diameter ranging from 2 .mu.m to 20 .mu.m in order to better
control the forward voltage (V.sub.F) and the light output power
(LOP), i.e., brightness. The first openings 161 of the current
spreading layer 130 are spaced apart from one another by a spacing
ranging from 1 .mu.m to 20 .mu.m. In this embodiment, each of the
first openings 161 has a diameter ranging from 2 .mu.m to 10 .mu.m
and the first openings 161 are spaced apart from one another by a
spacing ranging from 5 .mu.m to 20 .mu.m.
[0060] In addition, the LED device 10 further includes an extended
electrode 175 that is disposed on the current spreading layer 130
and that is electrically contacted with the second-type
semiconductor layer 123 through a portion of the first openings 161
of the current spreading layer 130. Since a contact resistance
between the extended electrode 175 and the second-type
semiconductor layer 123 is larger than a contact resistance between
the extended electrode 175 and the current spreading layer 130, the
current passing through the extended electrode 175 can be ensured
to flow through the current spreading layer 130 for current
spreading and then flow into the second-type semiconductor layer
123. In this way, the forward voltage (V.sub.F) can be lowered and
the light emitting efficiency can be increased.
[0061] The first insulating layer 141 and the reflective structure
150 are integrally formed as a reflective insulating member 153
which is disposed over the extended electrode 175 and the current
spreading layer 130. In addition, the reflective insulating member
153 is formed with the first penetrating hole 181 to expose the
first-type semiconductor layer 121, and is formed with the second
penetrating hole 182 to expose the extended electrode 175. The
first and second electrodes 171, 172 are formed on the reflective
insulating member 153. The first electrode 171 electrically
contacts with the first-type semiconductor layer 121 through the
first penetrating hole 181. The second electrode 172 electrically
contacts with the extended electrode 175 through the second
penetrating hole 182, and electrically connects to the second-type
semiconductor layer 123 through the current spreading layer
130.
[0062] In conclusion, by forming the current spreading layer 130,
the first insulating layer 141 and the reflective structure 150 as
an ODR structure, which has better reflectance than a conventional
metallic reflecting layer or DBR, the LED device 10 of this
disclosure can exhibit improved external light extraction
efficiency and brightness. In addition, by contacting the
reflective structure 150 with the current spreading layer 130
through the first through hole(s) 162 formed on the first
insulating layer 141, the forward voltage (V.sub.F) of the LED
device 10 can be maintained (i.e., without increasing the forward
voltage). By forming the first openings 161 on the current
spreading layer 130, the ohmic contact between the current
spreading layer 130 and the epitaxial layered structure 120 can be
further improved, and the optical absorption of the current
spreading layer 130 can be reduced so as to increase the brightness
of the LED device 10 of this disclosure.
[0063] In the description above, for the purposes of explanation,
numerous specific details have been set forth in order to provide a
thorough understanding of the embodiments. It will be apparent,
however, to one skilled in the art, that one or more other
embodiments maybe practiced without some of these specific details.
It should also be appreciated that reference throughout this
specification to "one embodiment," "an embodiment," an embodiment
with an indication of an ordinal number and so forth means that a
particular feature, structure, or characteristic may be included in
the practice of the disclosure. It should be further appreciated
that in the description, various features are sometimes grouped
together in a single embodiment, figure, or description thereof for
the purpose of streamlining the disclosure and aiding in the
understanding of various inventive aspects, and that one or more
features or specific details from one embodiment may be practiced
together with one or more features or specific details from another
embodiment, where appropriate, in the practice of the
disclosure.
[0064] While the disclosure has been described in connection with
what are considered the exemplary embodiments, it is understood
that this disclosure is not limited to the disclosed embodiments
but is intended to cover various arrangements included within the
spirit and scope of the broadest interpretation so as to encompass
all such modifications and equivalent arrangements.
* * * * *