U.S. patent application number 13/011674 was filed with the patent office on 2011-05-19 for side light emitting type semiconductor laser diode having dielectric layer formed on active layer.
This patent application is currently assigned to SAMSUNG LED CO., LTD.. Invention is credited to Kyoung-ho Ha, Han-youl Ryu.
Application Number | 20110116525 13/011674 |
Document ID | / |
Family ID | 37911043 |
Filed Date | 2011-05-19 |
United States Patent
Application |
20110116525 |
Kind Code |
A1 |
Ryu; Han-youl ; et
al. |
May 19, 2011 |
SIDE LIGHT EMITTING TYPE SEMICONDUCTOR LASER DIODE HAVING
DIELECTRIC LAYER FORMED ON ACTIVE LAYER
Abstract
Provided is a side light emitting type semiconductor laser diode
in which a dielectric layer is formed on an active layer. The side
light emitting type semiconductor laser diode includes an n-clad
layer, an n-light guide layer, an active layer and a p-light guide
layer sequentially formed on a substrate, and a dielectric layer
with a ridge structure formed on the p-light guide layer.
Inventors: |
Ryu; Han-youl; (Suwon-si,
KR) ; Ha; Kyoung-ho; (Seoul, KR) |
Assignee: |
SAMSUNG LED CO., LTD.
Suwon-si
KR
|
Family ID: |
37911043 |
Appl. No.: |
13/011674 |
Filed: |
January 21, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11545546 |
Oct 11, 2006 |
7899103 |
|
|
13011674 |
|
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|
|
Current U.S.
Class: |
372/46.01 |
Current CPC
Class: |
B82Y 20/00 20130101;
H01S 5/0655 20130101; H01S 2301/173 20130101; H01S 5/04257
20190801; H01S 5/2063 20130101; H01S 5/2222 20130101; H01S 5/24
20130101; H01S 5/0422 20130101; H01S 5/2231 20130101; H01S 5/34333
20130101 |
Class at
Publication: |
372/46.01 |
International
Class: |
H01S 5/42 20060101
H01S005/42 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 12, 2005 |
KR |
10-2005-0096159 |
Claims
1-4. (canceled)
5. A side light emitting type semiconductor laser diode comprising
a substrate; an n-clad layer disposed on the substrate; an n-light
guide layer disposed on the n-clad layer; an active layer disposed
on the n-light guide layer; a p-light guide layer disposed on the
active layer; a dielectric layer with a ridge structure disposed on
the p-light guide layer; and a current restriction region disposed
on both sides of the p-light guide layer.
6. The side light emitting type semiconductor laser diode of claim
5, further comprising a current restriction region disposed on the
upper surface of the n-light guide layer to restrict a current
applied to the active layer.
7. The side light emitting type semiconductor laser diode of claim
5, further comprising a p-contact layer interposed between the
p-light guide layer and the dielectric layer and a current
diffusion layer interposed between the p-light guide layer and the
p-contact layer.
8-13. (canceled)
14. The side light emitting type semiconductor laser diode of claim
6, wherein the current restriction layer is formed of one of
undoped AlGaN and p-AlGaN.
15. The side light emitting type semiconductor laser diode of claim
7, wherein the current diffusion layer is formed of AlGaN.
Description
[0001] CROSS-REFERENCE TO RELATED PATENT APPLICATION
[0002] This application claims the benefit of Korean Patent
Application No. 10-2005-0096159, filed on Oct. 12, 2005, in the
Korean Intellectual Property Office, the disclosure of which is
incorporated herein in its entirety by reference.
BACKGROUND OF THE DISCLOSURE
[0003] 1. Field of the Disclosure
[0004] The present disclosure relates to a semiconductor layer
diode, and more particularly, to a side light emitting type
semiconductor laser diode including a dielectric layer formed on an
active layer, and a p-conductive layer supplying current to both
sides of the dielectric layer and a method of manufacturing the
same.
[0005] 2. Description of the Related Art
[0006] Semiconductor laser diodes, currently used in light sources
of various information processing apparatuses, require high light
extraction efficiency versus an applied electric power to increase
information density. Accordingly, research into the optimization of
the structure of a laser diode has been conducted.
[0007] FIG. 1 is a cross-sectional view of a conventional
semiconductor laser diode. Referring to FIG. 1, an n-AlGaN layer 11
is formed on a substrate 10 and an n-AlGaN clad layer 12, an InGaN
active layer 13 having a Multi Quantum Wall (MQW) structure, a
p-AlGaN clad layer 14, a p-contact layer 15 and a p-electrode layer
16 are sequentially formed on the n-AlGaN layer 11. In addition, an
n-electrode layer 17 is formed on the region of the n-AlGaN layer
11 in a region where the n-AlGaN clad layer 12 is not formed.
[0008] In order to form the semiconductor laser diode illustrated
in FIG. 1, the n-AlGaN clad layer 12, the InGaN MQW active layer
13, the p-AlGaN clad layer 14, the p-contact layer 15 and the
p-electrode layer 16 are sequentially formed on the n-AlGaN layer
11. Then, semiconductor materials are removed from the region of
the n-AlGaN layer 11 where the n-electrode layer 17 is to be formed
to expose the n-AlGaN layer 11, and then the n-electrode layer 17
is formed.
[0009] The conventional semiconductor laser diode illustrated in
FIG. 1 has the following problems.
[0010] First, in the process of forming the semiconductor laser
diode shown in FIG. 1, while heat-treatment of the p-AlGaN clad
layer 14 is performed at a high temperature in a growth process,
segregation of indium (In) grown at a low temperature is performed
in the InGaN active layer 13 and thus, the quality of the MQW
structure of the InGaN active layer 13 may decline.
[0011] Second, doping materials using p-type impurities, for
example, Mg, may cause a lattice defect of the p-AlGaN clad layer
14, and thus optical loss is increased.
[0012] Third, due to diffusion of Mg in the p-AlGaN clad layer 14,
the quality of the MQW structure in the InGaN active layer 13 may
decline.
SUMMARY OF THE DISCLOSURE
[0013] The present disclosure provides a semiconductor laser diode
having a dielectric layer instead of a p-clad layer formed on an
active layer to improve optical characteristics of the
semiconductor laser diode.
[0014] According to an aspect of the present disclosure, there is
provided a side light emitting type semiconductor laser diode
including: a substrate; an n-clad layer disposed on the substrate;
an n-light guide layer disposed on the n-clad layer; an active
layer disposed on the n-light guide layer; a p-light guide layer
disposed on the active layer; and a dielectric layer with a ridge
structure disposed on the p-light guide layer.
[0015] A p-contact layer may be interposed between the p-light
guide layer and the dielectric layer.
[0016] A p-electrode layer may be disposed on the sides of the
dielectric layer.
[0017] An n-semiconductor layer may be interposed between the
substrate and the n-clad layer and an n-electrode layer may be
disposed on one portion of the n-semiconductor layer.
[0018] A current restriction region may be disposed on both sides
of the p-light guide layer.
[0019] A current restriction region may be disposed on the upper
surface of the n-light guide layer to restrict a current applied to
the active layer.
[0020] A current diffusion layer may be interposed between the
p-light guide layer and the p-contact layer.
[0021] The n-clad layer may be formed of Al.sub.xGaN(x.gtoreq.0).
The n-light guide layer may be formed of In.sub.xGaN(x.gtoreq.0).
The active layer may have a Multi Quantum Wall (MOW) structure
formed of In.sub.xGaN (x.gtoreq.0). The p-light guide layer may be
formed of In.sub.xGaN(x.gtoreq.0).
[0022] The dielectric layer may include at least one material
selected from the group consisting of SiO.sub.2, SiN.sub.x,
HfO.sub.x, AlN, Al.sub.2O.sub.3, TiO.sub.2, ZrO.sub.2, MnO, and
Ta.sub.2O.sub.5.
[0023] The p-contact layer may be formed of
In.sub.xGaN(x.gtoreq.0).
[0024] The current restriction layer may be formed of one of
undoped-AlGaN and p-AlGaN and the current diffusion layer may be
formed of AlGaN.
BRIEF DESCRIPTION OF THE DRAWINGS
[0025] The above and other features and advantages of the present
disclosure will become more apparent by describing in detail
exemplary embodiments thereof with reference to the attached
drawings in which:
[0026] FIG. 1 is a cross-sectional view of a conventional
semiconductor laser diode;
[0027] FIG. 2 is a cross-sectional view of a semiconductor laser
diode having a dielectric layer formed on an active layer according
to an embodiment of the present disclosure;
[0028] FIG. 3A is a cross-sectional view of a laser diode according
to an embodiment of the present disclosure in which a current
restriction region is formed on a p-light guide layer;
[0029] FIG. 3B is a cross-sectional view of a laser diode according
to an embodiment of the present disclosure in which a current
restriction layer is formed on the structure illustrated in FIG.
3A;
[0030] FIG. 4 is a cross-sectional view of a laser diode including
a current diffusion layer on the p-light guide layer in the basic
structure illustrated in FIG. 2;
[0031] FIG. 5 is a graph of the result of a simulation showing an
overlapping ratio of a dielectric layer and a laser light mode
oscillating in an active layer of the semiconductor laser diode of
an embodiment of the present disclosure and a p-clad layer and a
laser light mode oscillating in an active layer of a conventional
semiconductor laser diode; and
[0032] FIG. 6 is a graph of modal loss according to ridge width of
a dielectric layer having a ridge structure in a semiconductor
laser diode according to an embodiment of the present
disclosure.
DETAILED DESCRIPTION OF THE DISCLOSURE
[0033] The present disclosure will now describe more fully, with
reference to the accompanying drawings, exemplary embodiments of
the disclosure. The claimed invention may, however, be embodied in
many different forms and should not be construed as being limited
to the embodiments set forth herein; rather, these embodiments are
provided so that this disclosure will be thorough and complete, and
will fully convey the concept of the invention to those skilled in
the art. In the drawings, the thicknesses of layers and regions are
exaggerated for clarity. Like reference numerals in the drawings
denote like elements, and thus their descriptions will not be
repeated.
[0034] FIG. 2 is a cross-sectional view of a side light emitting
type semiconductor laser diode in which a dielectric layer 27 is
formed on an active layer according to an embodiment of the present
disclosure.
[0035] Referring to FIG. 2, an n-semiconductor layer 21 is formed
on a substrate 20 and an n-clad layer 22, an n-light guide layer
23, an active layer 24 and a p-light guide layer 25 are
sequentially formed on the n-semiconductor layer 21. Optionally, a
p-contact layer 26 can be further formed on the p-light guide layer
25. In addition, the dielectric layer 27 is formed on a central
region of the p-light guide layer 25 or the p-contact layer 26, and
a p-electrode layer 28 is formed at the sides of the dielectric
layer 27. An n-electrode layer 29 is formed on the remaining
portion of the n-semiconductor layer 21 where the n-clad layer 22
is not formed.
[0036] The n-semiconductor layer 21 and the n-clad layer 22 can
respectively be formed of Al.sub.xGaN (x.gtoreq.0). The n-light
guide layer 23 can be formed of In.sub.xGaN (x.gtoreq.0) and the
active layer 24 can have a Multi Quantum Wall (MQW) structure and
be formed of In.sub.xGaN (x.gtoreq.0). The p-light guide layer 25
can be formed of In.sub.xGaN(x.gtoreq.0) and the p-contact layer 26
can be formed of In.sub.xGaN(x.gtoreq.0).
[0037] In an embodiment of the present disclosure, the dielectric
layer 27 has a ridge structure on the p-light guide layer 25 or the
p-contact layer 26, and is formed of a dielectric material such as
SiO.sub.2, SiN.sub.x, HfO.sub.x, AlN, Al.sub.2O.sub.3, TiO.sub.2,
ZrO.sub.2, MnO or Ta.sub.2O.sub.5. The dielectric layer 27 plays a
role in guiding the light mode generated in the active layer 24 by
the current supplied to the p-electrode layer 28 and the
n-electrode layer 29. In order to oscillate the laser, the current
supplied to the active layer 24 is supplied through the p-electrode
layer 28 formed on both sides of the dielectric layer 27.
[0038] To increase the efficiency of the supply of current, a
current restriction region can be formed on the p-light guide layer
25 or the n-light guide layer 23. This is described below with
reference to FIGS. 3A through 3B.
[0039] FIG. 3A is a cross-sectional view of a laser diode according
to an embodiment of the present disclosure in which current
restriction regions 25a are formed in the p-light guide layer 25.
Referring to FIG. 3A, the n-semiconductor layer 21 is formed on the
substrate 20 and the n-clad layer 22, and the n-light guide layer
23, the active layer 24 and the p-light guide layer 25 are
sequentially formed on the n-semiconductor layer 21. Optionally,
the p-contact layer 26 can be further formed on the p-light guide
layer 25. In addition, the dielectric layer 27 is formed on the
central region of the p-light guide layer 25 or the p-contact layer
26, and the p-electrode layer 28 is formed at the sides of the
dielectric layer 27. The n-electrode layer 29 is formed on the
remaining portion of the n-semiconductor layer 21 where the n-clad
layer 22 is not formed. The structure herein is the same as the
basic structure illustrated in FIG. 2. However, in FIG. 3A, the
current restriction regions 25a are further formed in the p-light
guide layer 25.
[0040] The current restriction regions 25a are formed by injecting
a material such as H, B or NH.sub.3 into both sides of the p-light
guide layer 25 using implantation when the p-light guide layer 25
is formed. When the p-light guide layer 25 is optionally formed,
p-type impurities can be doped in the region excluding the current
restriction regions 25a. Thus, if the current is supplied through
the p-contact layer 28 formed on both sides of the dielectric layer
27, the current passes through a space between the current
restriction regions 25a of the p-light guide layer 25, instead of
through the current restriction regions 25a themselves, and then
reach the active layer 24. Consequentially, the current is mainly
supplied to the central region of the active layer 24, and thus
efficient laser oscillation can occur.
[0041] Moreover, if the current restriction regions 25a are formed
on both portions of the n-light guide layer 23, the current can be
supplied mainly to the central region of the active layer 24. That
is, if the material such as H, B or NH.sub.3 is injected into both
sides of the p-light guide layer 25 using implantation, or the
n-light guide layer 23 is optionally formed, n-type impurities can
be doped in the region excluding the current restriction regions
25a.
[0042] FIG. 3B is a cross-sectional view of a laser diode including
a current restriction layer 30. Referring to FIG. 3B, the current
restriction layer 30 is formed between the n-light guide layer 23
and the active layer 24 to restrict the route of the current
supplied from the n-electrode layer 29, instead of forming the
current restriction regions in the n-light guide layer 25. In
detail, after forming the n-light guide layer 23, undoped AlGaN or
p-AlGaN is supplied to the upper surface of the n-light guide layer
23 and the n-light guide layer 23 is exposed by etching the central
region of the undoped AlGaN or AlGaN. Then, the active layer 24 and
the p-light guide layer 25 are sequentially formed on the upper
surface of the etched region. Consequently, the active layer 24 is
grooved. Accordingly, the current supplied by the n-electrode layer
29 cannot pass through the current restriction layer 30, and thus
the current is supplied mainly to the central region of the active
layer 24 through the space formed in the current restriction layer
30. Thus, efficient laser oscillation can occur.
[0043] FIG. 4 is a cross-sectional view of a laser diode including
a current diffusion layer 31 on the p-light guide layer 25 in the
basic structure illustrated in FIG. 2.
[0044] Referring to FIG. 4, the n-semiconductor layer 21 is formed
on the substrate 20 and the n-clad layer 22, the n-light guide
layer 23, the active layer 24, the p-light guide layer 25 and the
current diffusion layer 31 are sequentially formed on the
n-semiconductor layer 21. Optionally, the p-contact layer 26 can be
further formed on the current diffusion layer 31. In addition, the
dielectric layer 27 is formed on the central region of the p-light
guide layer 25 or the p-contact layer 26, and the p-electrode layer
28 is formed at the sides of the dielectric layer 27. The
n-electrode layer 29 is formed on the remaining portion of the
n-semiconductor layer 21 where the n-clad layer 22 is not formed.
The current diffusion layer 31 can be formed of AlGaN, and the
current supplied through the p-electrode layer 28 is supplied to
the active layer 24 through the current diffusion layer 31. The
current diffusion layer 31 is thin (approximately 100 nm), and a
process of high temperature oxidation is either unnecessary or
performed for a very short time. Accordingly, the quality of the
MQW structure in segregation of indium (In) of the active layer 24
may not decline.
[0045] Hereinafter, the laser diode of an embodiment of the present
disclosure and a conventional laser diode will be compared with
reference to FIG. 5. FIG. 5 is a graph of the result of a
simulation showing an overlapping ratio of a dielectric layer and a
laser light mode oscillating in an active layer of the
semiconductor laser diode of an embodiment of the present
disclosure and a p-clad layer and a laser light mode oscillating in
an active layer of a conventional semiconductor laser diode. In a
conventional laser diode, AIGaN is used for the p-clad layer and
the refractive index of the p-clad layer is about 2.5. Referring to
FIG. 5, when the laser beam that oscillated in the active layer was
transmitted toward the sides of the active layer, the overlapping
ratio of the light mode to the p-clad layer, which was doped with
Mg as a p-type impurity, was over 20%, and thus optical loss was
low.
[0046] In addition, in the laser diode structure illustrated in
FIG. 3A, the overlapping ratio of the dielectric layer to the laser
oscillated in the active layer was investigated by using materials
with different refractive indexes to form the dielectric layer. It
was found that the overlapping ratio was less than 10% even when
the dielectric layer was formed of a material with a refractive
index of 2.5. Consequently, the laser diode structure of an
embodiment of the present disclosure showed a greater decrease in
optical loss than that of the conventional art.
[0047] FIG. 6 is a graph of modal loss according to ridge width of
a dielectric layer having a ridge structure in a semiconductor
laser diode according to an embodiment of the present disclosure.
FIG. 6 shows the results for a fundamental mode (0.sup.th mode) and
a 1st-order mode of an oscillated laser. In the semiconductor laser
diode according to an embodiment of the present disclosure
illustrated in FIG. 2, the optical loss occurs in the p-electrode
layer 28, which is formed of a metal material at the sides of the
dielectric layer 27 having the ridge structure. When the width of
the dielectric layer 27 is less than approximately 2 .mu.m, the
modal loss of the fundamental mode is small, below 20 cm.sup.-1. On
the other hand, since the loss of the 1st-order mode is high, a
high kink level exists due to the efficiency of the mode selection.
Thus, the laser oscillated in the active layer can be easily
emitted as a single transverse mode laser.
[0048] The semiconductor laser diode of the present disclosure has
the following advantages.
[0049] First, a characteristic decline of the active layer which
may occur in the growth process of the p-clad layer at a high
temperature can be prevented.
[0050] Second, optical loss due to diffusion of Mg, the p-type
doping material, can be prevented.
[0051] Third, the material constituting the dielectric layer can be
selected according to its refractive index.
[0052] Fourth, using a difference between the optical losses of the
fundamental mode of the oscillated laser in a metal contact and the
1st-order mode, an oscillation of high order mode laser can be
controlled.
[0053] While the present disclosure 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 disclosure as defined by
the following claims.
* * * * *