U.S. patent application number 16/380115 was filed with the patent office on 2019-08-01 for light-emitting device.
The applicant listed for this patent is EPISTAR CORPORATION. Invention is credited to Chun-WEI CHANG, Liang-Sheng CHI, Chen OU, Chih-Wei WU.
Application Number | 20190237628 16/380115 |
Document ID | / |
Family ID | 50232356 |
Filed Date | 2019-08-01 |
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United States Patent
Application |
20190237628 |
Kind Code |
A1 |
OU; Chen ; et al. |
August 1, 2019 |
LIGHT-EMITTING DEVICE
Abstract
A light-emitting device includes: a light-emitting stack formed
on a first conductivity type contact layer and including an active
layer and a second conductivity type semiconductor layer on the
active layer; a first trench dividing the light-emitting stack into
a first portion and a second portion, wherein the first trench
includes a bottom exposing a top surface of the first conductivity
type contact layer; a non-conductive material layer formed in the
first trench and being a film conformal to a profile of the first
trench; a connecting layer formed in the first trench and
electrically connecting the first and the second portions of the
light-emitting stack, wherein the connecting layer is a film
conformal to a profile of the non-conductive material layer; and a
first electrode formed on the first conductivity type contact layer
and electrically connected to the first conductivity type
semiconductor layer.
Inventors: |
OU; Chen; (Hsinchu, TW)
; CHI; Liang-Sheng; (Hsinchu, TW) ; CHANG;
Chun-WEI; (Hsinchu, TW) ; WU; Chih-Wei;
(Hsinchu, TW) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
EPISTAR CORPORATION |
Hsinchu |
|
TW |
|
|
Family ID: |
50232356 |
Appl. No.: |
16/380115 |
Filed: |
April 10, 2019 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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13614405 |
Sep 13, 2012 |
10290773 |
|
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16380115 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01L 33/42 20130101;
H01L 33/38 20130101; H01L 33/08 20130101; H01L 33/14 20130101 |
International
Class: |
H01L 33/42 20060101
H01L033/42; H01L 33/14 20060101 H01L033/14; H01L 33/08 20060101
H01L033/08 |
Claims
1. A light-emitting device, comprising: a substrate; a first
conductivity type contact layer on the substrate; a light-emitting
stack on the first conductivity type contact layer, comprising an
active layer and a second conductivity type semiconductor layer on
the active layer; a first trench dividing the light-emitting stack
into a first portion and a second portion, wherein each of the
first portion and the second portion comprises a portion of the
active layer and a portion of the second conductivity type
semiconductor layer and the first trench comprises a bottom
exposing a top surface of the first conductivity type contact
layer; a non-conductive material layer formed in the first trench
and being a film conformal to a profile of the first trench; a
connecting layer formed in the first trench and electrically
connecting the first and the second portions of the light-emitting
stack, where in the connecting layer is a film conformal to a
profile of the non-conductive material layer; and a first electrode
formed on the first conductivity type contact layer and
electrically connected to the first conductivity type semiconductor
layer.
2. The light-emitting device as claimed in claim 1, further
comprising a transparent conductive layer on the light-emitting
stack.
3. The light-emitting device as claimed in claim 2, further
comprising a second trench dividing the transparent conductive
layer into a first block and a second block.
4. The light-emitting device as claimed in claim 3, wherein the
non-conductive material layer is conformal to a profile of the
second trench.
5. The light-emitting device as claimed in claim 3, wherein the
connecting layer contacts the first block and the second block.
6. The light-emitting device as claimed in claim 1, further
comprising a first conductivity type semiconductor layer between
the first conductivity type contact layer and the active layer, and
the first conductivity type contact layer comprises the same
material as that of the first conductivity type semiconductor
layer.
7. The light-emitting device as claimed in claim 6, wherein the
first conductivity type contact layer has a higher doping level
than that of the first conductivity type semiconductor layer.
8. The light-emitting device as claimed in claim 1, wherein the
connecting layer comprises a first segment between the first
portion and the second portion and a secondary segment on one of
the first portion and the second portion.
9. The light-emitting device as claimed in claim 8, wherein a shape
of the secondary segment comprises a curve.
10. The light-emitting device as claimed in claim 1, wherein a
shape of the light-emitting device from its top view is a rectangle
having a longitudinal direction, and the first electrode is
disposed near one end of the longitudinal direction of the
rectangle.
11. The light-emitting device as claimed in claim 10, wherein a
ratio of a length to a width of the rectangle is not smaller than
2.
12. The light-emitting device as claimed in claim 6, wherein the
first conductivity type contact layer is exposed by the first
trench.
13. The light-emitting device as claimed in claim 1, further
comprising a second electrode on one of the first portion and the
second portion.
14. The light-emitting device as claimed in claim 13, wherein the
second electrode comprises the same material as that of the
connecting layer.
15. The light-emitting device as claimed in claim 1, wherein a
first current flow through the first portion is equal to a second
current flow through the second portion when driving the
light-emitting device.
16. The light-emitting device as claimed in claim 2, wherein the
conductivity of the connecting layer is larger than the
conductivity of the transparent conductive layer.
17. The light-emitting device as claimed in claim 3, wherein a
shape of the first trench and a shape of the second trench in a
cross section of the light-emitting device are different.
18. The light-emitting device as claimed in claim 3, wherein the
first trench comprises a first width along a horizontal direction
perpendicular to a stacking direction of the first conductivity
type semiconductor layer, the active layer and the second
conductivity type semiconductor layer from a cross section view of
the light-emitting device, and the second trench comprises a second
width along the horizontal direction perpendicular to the stacking
direction from the cross section view of the light-emitting device,
and the second width is larger than the first width.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application a continuation application of U.S. patent
application Ser. No. 13/614,405, entitled "LIGHT-EMITTING DEVICE",
filed on Sep. 13, 2012, which is incorporated by reference herein
in its entirety.
TECHNICAL FIELD
[0002] The application relates to a light-emitting device, in
particular to a light-emitting diode with uniform light
emission.
DESCRIPTION OF BACKGROUND ART
[0003] A light-emitting diode (LED) is known for its high energy
efficiency and is introduced to various fields of use. The theory
for a light-emitting diode (LED) to emit light is that when a
forward voltage power is applied to a p-n junction, the electrons
are driven from the n-type semiconductor and the holes are driven
from the p-type semiconductor, and these carriers are combined in
the active layer to emit light. The efficiency of an LED depends on
the combination rate of the electrons from the n-type semiconductor
and the holes from the p-type semiconductor. However, due to the
poor current spreading, especially in the p-type semiconductor, the
efficiency is reduced. An electrode with an extending part such as
a finger-type electrode is commonly used to improve the poor
current spreading. In addition, a transparent conductive layer is
disposed between the finger-type electrode and the p-type
semiconductor as an ohmic contact layer to improve the current
spreading.
[0004] FIG. 1 is a schematic structure diagram of a conventional
light-emitting diode without the finger-type p-electrode. FIG. 1A
is the top view, and FIG. 1B is the cross-sectional view along the
line W-W'. As shown in FIG. 1, a conventional light-emitting device
10 comprises a substrate 100, a light-emitting stack 110, a
transparent conductive layer 104, and two electrodes 105, 106. The
light-emitting stack 110 comprises a first conductivity type
semiconductor layer 101, a second conductivity type semiconductor
layer 103, and an active layer 102 between the first conductivity
type semiconductor layer 101 and the second conductivity type
semiconductor layer 103. For example, the first conductivity type
semiconductor layer 101 is n-type, and the second conductivity type
semiconductor layer 103 is p-type. The first electrode 105 is
electrically connected to the first conductivity type semiconductor
layer 101, and the second electrode 106 is electrically connected
to the transparent conductive layer 104. When an external power
source is supplied to the light-emitting device 10 from the two
electrodes 105, 106, the condition of electrons flow (the reverse
of the current/holes flow) from the first electrode 105 to the
second electrode 106 is shown as the arrow lines indicate. As the
second electrode 106 is not an electrode with an extending part, a
current crowding phenomenon occurs and there is almost no electrons
flow in the area A which is not under the second electrode 106.
This phenomenon results in a non-uniform light emission and low
luminous efficiency.
[0005] To solve the problem described above, a conventional
light-emitting diode with the finger-type p-electrode shown in FIG.
2 is provided. FIG. 2A is the top view, and FIG. 2B is the
cross-sectional view along the line W-W'. The conventional
light-emitting device 20 is substantially the same as the
light-emitting device 10, except that the second electrode 206 is a
finger-type electrode, which comprises an extending part 206a in
addition to the main part 206b. Other elements, such as a substrate
200, a light-emitting stack 210, a first conductivity type
semiconductor layer 201, an active layer 202, a second conductivity
type semiconductor layer 203, and a transparent conductive layer
204, are the same as those shown in FIG. 1, and are not discussed
again.
[0006] As illustrated in FIG. 2, the extending part 206a is
introduced to solve the current crowding problem. When an external
power source is supplied to the light-emitting device 20 from the
two electrodes 205, 206, the condition of electrons flow (the
reverse of the current/holes flow) from the first electrode 205 to
the second electrode 206 is shown as the arrow lines indicate.
Because the second electrode 206 is a finger-type electrode, the
current/holes is(are) spread by the extending part 206a, and the
deficiency which there is almost no electrons flow in the area A in
FIG. 1 is improved. However, as shown in FIG. 2, it is observed
that electrons flow in that area A is a majority part, and only a
few of electrons flow through the area B in FIG. 2.
SUMMARY OF THE DISCLOSURE
[0007] A light-emitting device is disclosed and comprises: a
substrate; a first conductivity type contact layer on the
substrate; a light-emitting stack on the first conductivity type
contact layer, comprising an active layer and a second conductivity
type semiconductor layer on the active layer; a first trench
dividing the light-emitting stack into a first portion and a second
portion, wherein each of the first portion and the second portion
comprises a portion of the active layer and a portion of the second
conductivity type semiconductor layer and the first trench
comprises a bottom exposing a top surface of the first conductivity
type contact layer; a non-conductive material layer formed in the
first trench and being a film conformal to a profile of the first
trench; a connecting layer formed in the first trench and
electrically connecting the first and the second portions of the
light-emitting stack, where in the connecting layer is a film
conformal to a profile of the non-conductive material layer; and a
first electrode formed on the first conductivity type contact layer
and electrically connected to the first conductivity type
semiconductor layer.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] FIG. 1 is a schematic structure diagram of a conventional
light-emitting diode without the finger-type electrode with the
electrons flow. FIG. 1A is the top view, and FIG. 1B is the
cross-sectional view along the line W-W'.
[0009] FIG. 2 is a schematic structure diagram of a conventional
light-emitting diode with the finger-type electrode with the
electrons flow. FIG. 2A is the top view, and FIG. 2B is the
cross-sectional view along the line W-W'.
[0010] FIG. 3 is a schematic structure diagram of the
light-emitting diode in accordance with the first embodiment of the
present application. FIG. 3A is the top view, and FIG. 3B is the
cross-sectional view along the line W-W'. FIG. 3C shows the
equivalent resistance model of the light-emitting device shown in
FIG. 3A (or 3B).
[0011] FIG. 4 is a schematic structure diagram of the
light-emitting diode in accordance with the second embodiment of
the present application. FIG. 4A is the top view, and FIG. 4B is
the cross-sectional view along the line W-W'.
[0012] FIG. 5 is a schematic structure diagram of the
light-emitting diode in accordance with the third embodiment of the
present application. FIG. 5A is the top view, and FIG. 5B is the
cross-sectional view along the line W-W'.
[0013] FIG. 6 is a cross-sectional view along the line W-W' in FIG.
5A of the light-emitting diode in accordance with the fourth
embodiment of the present application.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0014] FIG. 3 illustrates the first embodiment of present
application. FIG. 3A is the schematic structure diagram in the top
view, and FIG. 3B is the cross-sectional view along the line W-W'.
The light-emitting device 30 comprises a substrate 300, a first
conductivity type contact layer 311, a light-emitting stack 310, a
conductive structure 320, and two electrodes 305, 306. The
substrate 300 is a monolithic substrate and, for example, is a
sapphire substrate. The light-emitting stack 310 comprises a first
conductivity type semiconductor layer 301, a second conductivity
type semiconductor layer 303, and an active layer 302 between the
first conductivity type semiconductor layer 301 and the second
conductivity type semiconductor layer 303. For example, in this
embodiment the first conductivity type semiconductor layer 301 is
n-type, and the second conductivity type semiconductor layer 303 is
p-type. The light-emitting stack 310 is a stack of semiconductor
layers which can be formed by conventional epitaxy technology with
proper doping if necessary. For example, materials for each
semiconductor layer is composition of
Al.sub.xIn.sub.yGa.sub.(1-x-y)N (0.ltoreq.x.ltoreq.1,
0.ltoreq.y.ltoreq.1, 0.ltoreq.x+y.ltoreq.1).
[0015] The conductive structure 320 comprises a transparent
conductive layer 321 of a first conductive material over the
light-emitting stack 310, and a connecting layer 322 of a second
conductive material. The transparent conductive layer 321 comprises
a first block 321a and a second block 321b which is adjacent to but
separated from the first block 321a by a first trench 307. That is,
the first trench 307 divides the transparent conductive layer 321
into the first block 321a and the second block 321b. The first
trench 307 may be formed by an etching process to remove the part
between the first block 321a and the second block 321b of the
transparent conductive layer 321. In this embodiment, a
non-conductive material such as SiN.sub.x, SiO.sub.x, and SOG is
further provided and fills the first trench 307. In this
embodiment, the transparent conductive layer 321 may comprise a
transparent conductive oxide layer, for example, ITO (Indium Tin
Oxide), IZO (Indium Zinc Oxide), ZTO (Zinc Tin Oxide), AZO
(Al-doped ZnO), GZO (Ga-doped ZnO), IGZO (Indium Gallium Zinc
Oxide), CTO (Cadmium Stannate, Cd.sub.2SnO.sub.4), ZTO (Zinc
Stannate, Zn.sub.2SnO.sub.4), and CIO (Cadmium Indate,
CdIn.sub.2O.sub.4).
[0016] The connecting layer 322 over the transparent conductive
layer 321 comprises a second conductive material and electrically
connects the two blocks 321a and 321b of the transparent conductive
layer 321. The second conductive material comprises conductivity
which is different from that of first conductive material of the
transparent conductive layer 321. Preferably, the second conductive
material comprises conductivity greater than that of the first
conductive material. For example, in this embodiment the connecting
layer 322 may comprises a metal material, or metal alloy or a
mixture thereof. The metal material may comprise copper (Cu),
aluminum (Al), indium (In), tin (Sn), gold (Au), platinum (Pt),
zinc (Zn), silver (Ag), titanium (Ti), lead (Pb), palladium (Pd),
germanium (Ge), nickel (Ni), chromium (Cr), cadmium (Cd), and
cobalt (Co). The first block 321a and the second block 321b of the
transparent conductive layer 321 are electrically connected by the
connecting layer 322 so that the first block 321a, the second block
321b, and the connecting layer 322 form a first current path.
[0017] The first conductivity type contact layer 311 is disposed
between the substrate 300 and the first conductivity type
semiconductor layer 301. The conductivity of the first conductivity
type contact layer 311 is different from the conductivity of the
first conductivity type semiconductor layer 301. In this
embodiment, the conductivity of the first conductivity type contact
layer 311 is greater than the conductivity of the first
conductivity type semiconductor layer 301. For example, the
conductivity of the first conductivity type contact layer 311
comprises the same material as that of the first conductivity type
semiconductor layer 301, but has a higher impurity doping level
than that of the first conductivity type semiconductor layer 301.
In this embodiment, the first conductivity type semiconductor layer
301 is doped to a concentration of about
5.times.10.sup.17(atoms/cm.sup.3), while the first conductivity
type contact layer 311 is doped to a concentration of about
5.times.10.sup.18(atoms/cm.sup.3). The first electrode 305 is
electrically connected to the first conductivity type contact layer
311 to be electrically connected to the first conductivity type
semiconductor layer 301, and the second electrode 306 is
electrically connected to the conductive structure 320, or more
specifically to the second block 321b of the transparent conductive
layer 321 to be electrically connected to the second conductivity
type semiconductor layer 303. The second electrode 306 may be
formed simultaneously with the connecting layer 322. That is, the
second electrode 306 comprises the second conductive material.
[0018] FIG. 3C shows an equivalent resistance model of the
light-emitting device 30 shown in FIG. 3B. The equivalent
resistance model of the light-emitting device 30 is derived from
the resistance of each part of the light-emitting device 30 and
current flow paths between the two electrodes 305, 306 shown in
FIG. 3B. When an external power source is supplied to the
light-emitting device 30 from the two electrodes 305, 306, the
current (/holes) is (are) supplied from the second electrode 306 to
the second block 321b. Because the first trench 307 divides the
transparent conductive layer 321 into the first block 321a and the
second block 321b, the supplied current is divided into two paths.
In one current path, the current flows through the second block
321b, the connecting layer 322, and the first block 321a
sequentially, and then the current flows into a portion of the
light-emitting stack 310 which is substantially under the first
block 321a, and finally the current flow through a portion of the
first conductivity type contact layer 311 (with a resistance Rc) to
the first electrode 305. In the other current path, the current
flows through the second block 321b, and then the current flows
directly into the portion of the light-emitting stack 310
substantially under the second block 321b, and the current flows
through substantially the whole first conductivity type contact
layer 311 (with a resistance Rc+Rd), and finally the current flow
to the first electrode 305. Thus, the light-emitting device 30 is
divided into two diodes in the equivalent circuit model. One is the
portion of the light-emitting stack 310 which is substantially
under the first block 321a, and the other is the portion of the
light-emitting stack 310 substantially under the second block 321b,
as marked by rectangles D1 and D2, respectively. The two diodes D1
(with an internal resistance Rd1) and D2 (with an internal
resistance Rd2) form two light-emitting diodes in parallel
connection between the first electrode 305 and the second electrode
306.
[0019] The resistance for each part of the light-emitting device 30
is shown by a resistor. For example, the resistance for a portion
of the first conductivity type contact layer 311 which is
substantially under the first block 321a is indicated by a resistor
Rc, and the resistance for a portion of the first conductivity type
contact layer 311 which is substantially under the second block
321b is indicated by a resistor Rd. The equivalent resistance model
of the light-emitting device 30 is therefore shown as FIG. 3C.
[0020] The first block 321a, the second block 321b, and the
connecting layer 322 form a resistor R1 (and R1=Ra+Rt+Rb) serially
connected with the diode D1 and the second electrode 306. The
second block 321b forms a resistor R2(=Rb) serially connected with
the diode D2 and the second electrode 306. A resistor R3(=Rc) is
serially connected with the diode D1 and the first electrode 305.
In addition, as the first electrode 305 does not comprise any
extending electrode, for the diode D2, the current flows through
substantially the whole first conductivity type contact layer 311
(with a resistance Rc+Rd) before entering the first electrode 305.
That is, a resistor R4(=Rc+Rd) is substantially in serial
connection with the diode D2 and the first electrode 305. When the
total serial resistance for the respective current paths through
the two diodes D1 and D2 are compared, obviously, the resistor
R1(=Ra+Rt+Rb) for the current path through the diode D1 is larger
than the resistor R2(=Rb) for the current path through the diode
D2. However, the resistor R3(=Rc) for the current path through the
diode D1 is smaller than the resistor R4(=Rc+Rd) for the current
path through the diode D2. The person of ordinary skill in the art
therefore can modify the structure of the light-emitting device 30
so that the respective total serial resistances for the two current
paths through the diodes D1 and D2 are substantially the same.
Because the two diodes D1 and D2 form two light-emitting diodes in
parallel connection between the first electrode 305 and the second
electrode 306, a current flow through the diode D1 is substantially
equal to that through the diode D2, that is, a current flow through
the portion of the light-emitting stack 310 which is substantially
under the first block 321a is substantially equal to a current flow
through the portion of the light-emitting stack 310 substantially
under the second block 321b. This solves the current crowding
problem and brings a uniform light emission and high luminous
efficiency. The modification of the structure of the light-emitting
device 30 can be, for example, through the selection of the
materials or the dimensions of the first block 321a, the second
block 321b, and the connecting layer 322.
[0021] As the above illustration, this embodiment is useful to
solve the current crowding problem when the light-emitting device
comprises a rectangular shape from the top view, and especially
useful when the first electrode is disposed substantially at one
end along the longitudinal direction of the rectangle, as shown in
FIG. 3A. It is useful to solve the current crowding problem when a
ratio of the length to the width of the rectangle is not smaller
than 2. As shown in FIG. 3A, the first block 321a and the second
block 321b are arranged along the longitudinal direction of the
rectangle, and the connecting layer 322 is extending along the
longitudinal direction of the rectangle in this embodiment.
[0022] For a light-emitting device comprising a longer rectangle,
that is, a rectangle with a higher ratio of the length to the
width, the above first embodiment can be employed by analogy to
divide the transparent conductive layer 321 into more blocks, and
the whole light-emitting stack 310 is divided into more than two
portions to form more diodes in the equivalent circuit model,
wherein each of which constitutes a current path between the two
electrodes. FIG. 4 illustrates the second embodiment of present
application. FIG. 4A is the schematic structure diagram in the top
view, and FIG. 4B is the cross-sectional view along the line W-W'.
Three different top view layouts: (a), (b), and (c) are provided in
FIG. 4A, and the cross-sectional views cut along the W-W' line for
each layouts are the same and shown as FIG. 4B. The element
corresponding to the same element in FIG. 3 is labeled with the
same label code except that the first digit is changed from "3" to
"4". For example, element 400 in FIG. 4 is a substrate
corresponding to the substrate 300 in FIG. 3. Other elements are a
light-emitting stack 410, a first conductivity type semiconductor
layer 401, an active layer 402, a second conductivity type
semiconductor layer 403, and a first conductivity type contact
layer 411. The light-emitting device 40 is substantially the same
as the light-emitting device 30 shown in FIG. 3, except that the
transparent conductive layer 421 of the conductive structure 420
comprises one more block than the light-emitting device 30 does.
That is, the transparent conductive layer 421 comprises three
blocks, which is the first block 421a, the second block 421b, and
the third block 421c. In this embodiment, the connecting layer 422
comprises two segments 422a and 422b. The first trench 407 is
formed between every two adjacent blocks of the transparent
conductive layer 421. So in this embodiment, the light-emitting
device 40 is divided into three portions to form three
parallel-connected diodes in the equivalent circuit model, and each
of which constitutes a current path between electrodes 405, 406 as
shown in FIG. 4B. As previous illustration in FIG. 3, it is easy
for the person of ordinary skill in the art to modify the structure
of the light-emitting device 40 so that the current flows through
the three paths are substantially equal. It is noted that it is
possible for the person of ordinary skill in the art to make some
changes for the connecting layer 422. As shown in the (b) layout in
FIG. 4A, the connecting layer 422 may comprise more than one
segment between every two adjacent blocks of the transparent
conductive layer 421 to electrically connect the two adjacent
blocks. As shown in the (c) layout in FIG. 4A, the connecting layer
422 may further comprise a secondary segment 422' along a direction
different from the longitudinal direction. In this embodiment, the
secondary segment 422' is substantially perpendicular to the
segment 422 at the joint. In other embodiment, the shape of the
secondary segment 422' may comprise a curve.
[0023] FIG. 5 illustrates the top view of the third embodiment of
present application, and FIG. 5B is the cross-sectional view. Three
different top view layouts: (a), (b), and (c) are provided in FIG.
5A, and the cross-sectional views cut along the W-W' line for each
layouts are the same and shown in FIG. 5B. The element
corresponding to the same element in FIG. 4 (or FIG. 3) is labeled
with the same label code except that the first digit is changed
from "4" to "5". For example, element 500 in FIG. 5 is a substrate
corresponding to the substrate 400 in FIG. 4 (or the substrate 300
in FIG. 3.). Other elements are a conductive structure 520, a
connecting layer 522, two segments 522a and 522b, and a secondary
segment 522'. The light-emitting device 50 is substantially the
same as the light-emitting device 40 shown in FIG. 4, except that
there is a second trench 507a under the first trench 507. The
second trench 507a extends downward and through the light-emitting
stack 510 and divides the light-emitting stack into three portions:
a first portion substantially under the first block 521a, a second
portion substantially under the second block 521b, and a third
portion substantially under the third block 521c. Each portion
comprises the first conductivity type semiconductor layer 501, the
active layer 502 over the first conductivity type semiconductor
layer 501, and the second conductivity type semiconductor layer 503
over the active layer 502. The three portions form three diodes in
parallel connection and are disposed between the first electrode
505 and the second electrode 506. The second trench 507a may be
formed before or after forming the transparent conductive layer
521. When the second trench 507a is formed after the transparent
conductive layer 521 is formed, only one etch mask (ex.
photo-resistor) is used, and the second trench 507a and the first
trench 507 can be formed substantially at the same time by one
etching process. A mesa etch process can also be performed to
expose a part of the first conductivity type contact layer 511
simultaneously with the formation of the trenches. In another
embodiment, the second trench 507a is formed by a first etching
process with a first etch mask (ex. photo-resistor). Next, the
transparent conductive layer 521 is formed while part of the
transparent conductive layer 521 fills into the second trench 507a.
Afterwards, another etch mask (photo-resistor) is formed on the
transparent conductive layer 521, and a second etching process is
performed to form the first trench 507 and remove part of the
transparent conductive layer 521 that fills into the second trench
507a. Similarly, a mesa etch process can also be performed to
expose a part of the first conductivity type contact layer 511 with
the first etching process simultaneously.
[0024] FIG. 6 illustrates the fourth embodiment of present
application, which is a modification of the third embodiment. FIG.
6 shows the cross-sectional view along the line W-W' in FIG. 5A,
and is corresponding to the cross-sectional view of FIG. 5B.
[0025] The element corresponding to the same element in FIG. 5B is
labeled with the same label code except that the first digit is
changed from "5" to "6". For example, element 600 in FIG. 6 is a
substrate corresponding to the substrate 500 in FIG. 5B. Other
elements are a first conductivity type contact layer 611, a first
conductivity type semiconductor layer 601, an active layer 602, a
second conductivity type semiconductor layer 603, a first electrode
605, a second electrode 606, a conductive structure 620, a
transparent conductive layer 621, a first block 621a, a second
block 621b, a third block 621c, and two segments 622a and 622b. The
light-emitting device 60 is substantially the same as the
light-emitting device 50 shown in FIG. 5, except that the trenches
and the connecting layer are modified. In this embodiment, as FIG.
6 shows, the non-conductive material layer comprising the first
part 607' formed in the first trench and the second part 607a'
formed in the second trench is a film structure conformal to the
profile of the first trench and the second trench. That is, the
non-conductive material does not completely fill the trenches, and
the connecting layer 622 is also formed to be a film conformal to
the profile of the non-conductive material.
[0026] Though the embodiments described above are illustrated by a
horizontal type LED and specific materials, it will be apparent
that other alternatives, modifications and materials may be made to
the embodiments without escaping the spirit and scope of the
application.
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