JP3260489B2 - Semiconductor light emitting device and method of manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor light emitting device which emits light by current injection, and more particularly, to providing an electrode on a side surface of one or more ridges provided on a light emitting surface. Accordingly, the present invention relates to a semiconductor light emitting device having an electrode structure that does not hinder light emission and a method for manufacturing the same.

[0002]

2. Description of the Related Art A semiconductor device which emits light by current injection is:
Light emitting diodes (hereinafter abbreviated as LEDs) and semiconductor lasers are known and are used in many fields such as communication transmission and display. Light emitting diodes were first commercialized as infrared LEDs, but later red LEDs were developed and opened up for display. Further, in order to meet various display requirements, yellow, green, and blue LEDs having a shorter emission wavelength than red have been developed.

[0003] Conventionally, the active layer and the cladding layer have A
A red LED device using lGaAs has been made.
In order to shorten the emission wavelength of the LED and further increase the brightness, a conventional A
GaInP and AlGaInP, semiconductor materials having a region of direct transition to shorter wavelengths compared to lGaAs
Is attracting attention.

FIG. 7 shows the GaInP or AlGaI.
An example of a semiconductor light emitting device using nP is shown. This semiconductor light emitting device has an n-AlG substrate on an n-GaAs substrate 1002.
aInP cladding layer 1003, GaInP active layer 100
4. After forming a p-AlGaInP cladding layer 1005 sequentially, a GaAs contact layer 1006 and an n-side electrode 1
001 and a p-side electrode 1007 are formed.

By applying a negative voltage to the n-side electrode 1001 and a positive voltage to the p-side electrode 1007 of this semiconductor light emitting device,
From the n-AlGaInP cladding layer 1003, electrons, p-
Holes are injected from the AlGaInP cladding layer 1005 into the GaInP active layer 1004, respectively. And
Due to the recombination of electrons and holes in the GaInP active layer 1004, light having a wavelength corresponding to the band gap is generated.
-Light is transmitted through the AlGaInP cladding layer 1005 and extracted from the upper portion or the side surface of the device.

[0006]

In the case of a GaInP-based semiconductor light emitting device, a GaAs substrate generally used absorbs an emission wavelength.
It is important to increase the efficiency of extracting light upward.
However, in the case of the light emitting device shown in FIG.
007, since the contact layer 1006 does not transmit light,
Light generated immediately below the electrode in the active layer 1004 is blocked by the p-side electrode 1007 and cannot be extracted to the upper part. Further, since a current is injected only from the p-side electrode 1007 into the wide active layer 1004, a current 1020 having a higher current density flows immediately below the electrode that does not transmit light, which causes a problem of lowering luminous efficiency. there were.

In order to improve the luminous efficiency and the luminous intensity, it is necessary to uniformly diffuse the current injected from the p-side electrode 1007 into a portion of the active layer 1004 where the p-side electrode 1007 does not exist at the top. It is. As a countermeasure against this, it is conceivable to lower the resistance of the p-AlGaInP cladding layer 1005. However, in general, AlG
aInP is difficult to do p-type high doping and low resistance.

As another countermeasure, p-AlGaInP
A method of providing a current spreading layer for spreading a current above the cladding layer 1005 is also conceivable. FIG. 8 shows an example. By providing the current diffusion layer 1009, the current 102
0 easily spreads over the entire surface of the element. Current spreading layer 1009
Since there is a need to transmit light emitted from the active layer, the band gap needs to be large to some extent and the resistance must be low, so that there are few suitable materials. Although it is conceivable to use AlGaAs as the current diffusion layer, it is necessary to increase the Al mixed crystal ratio in order to make the band gap larger than the energy of the emission wavelength. On the other hand, AlGaAs
It is difficult to achieve a high Al mixed crystal ratio and a low resistance at the same time even in the s system. In order to shorten the oscillation wavelength, GaIn
When Al is added to the P active layer 1004, a material having a larger band gap is required.
s cannot be used.

Further, another countermeasure method will be described. FIG. 9 (a),
(B) shows a conventional example in which a comb-shaped electrode 1010 is formed in order to allow a current to flow uniformly over the entire surface of the element. In this example, a current can be uniformly supplied to the entire device without using a current diffusion layer. However, as in the previous example, it is impossible to extract light emitted immediately below the electrode to the upper side of the element.

In view of the above problems, an object of the present invention is to provide an electrode structure capable of uniformly injecting a current into a semiconductor light emitting device over the entire surface of the device without blocking light from a light emitting layer. To provide a semiconductor light emitting device.

[0011]

In order to solve the above problems, the present invention has the following arrangement. That is, the present invention
In a semiconductor light emitting device in which a cladding layer, an active layer, and a cladding layer are sequentially formed on a semiconductor substrate, a ridge is formed on an upper surface of the device, which is a light emitting surface, and at least one side of the ridge is substantially perpendicular to the upper surface of the device. A semiconductor light emitting device having electrodes formed thereon. Further, in the present invention, a contact layer can be provided between the side surface and the electrode. Further, in the present invention, a plurality of ridges formed on the light emitting surface are connected to each other, and a common electrode connected to the side electrode may be formed on a part of the upper surface of the element. Also, the present invention provides a method for forming a clad on a semiconductor substrate.
Semiconductor light-emitting device in which a layer, an active layer, and a cladding layer are sequentially formed
A ridge is formed on the upper surface of the device, which is a light emitting surface,
In order not to block the light emitted from the active layer, the ridge
An electrode is formed on at least one side of the
A plurality of formed ridges are formed by connecting a plurality of
Form a common electrode connected to the side electrode on part of the top surface of the device
A semiconductor light-emitting element is provided below the common electrode with a semiconductor layer of a different conductivity type or high resistance from that of the lower adjacent layer. In this semiconductor light emitting device
Can have a contact layer between the side and the electrode.
Wear. Under the common electrode, a semiconductor layer having a different conductivity type or high resistance from the lower adjacent layer can be provided.

The present invention also relates to a manufacturing method for forming a contact layer and / or an electrode on at least one side face of a plurality of ridges formed continuously.
Forming a contact layer and / or an electrode on the side surface of the ridge by injecting a material obliquely to the surface of the semiconductor light emitting element so that an adjacent ridge serves as a mask. This is a method for manufacturing a semiconductor light emitting device characterized by the following. Also, the present invention provides a
Form electrodes on at least one side of the formed ridge
In the manufacturing method, the cladding layer on the semiconductor substrate,
A step of sequentially forming an active layer and a cladding layer;
The layer has a different conductivity type or high resistance half from that of the adjacent layer below.
Forming a conductive layer as a sacrificial layer and forming an adjacent ridge
So that the surface of the semiconductor light emitting element is
To inject material from an oblique direction to form electrodes on the sides of the ridge.
And a common electrode connected to the side electrode is part of the upper surface of the element.
Forming the ridge and selectively etching the ridge.
Removing only the sacrificial layer of
This is a method for manufacturing a semiconductor light emitting device.

[0013]

According to the above arrangement, the light emitted from the active layer is emitted outside without being absorbed by the contact layer or the electrode. In addition, a current can be uniformly applied to the entire surface of the element without using a current diffusion layer or the like. In this case, the current is radiated outside without being absorbed by the contact layer or the electrode. Therefore, the luminous efficiency and the luminous intensity of the light emitting element are increased.

When the structure is formed, a contact layer and / or an electrode are formed obliquely so that the adjacent ridge shape itself becomes a mask. Or both are not created and do not need to be removed later.
Further, by providing the sacrificial layer on the top of the ridge from which light is emitted, the contact layer and / or the electrode formed on the sacrificial layer can be removed by a lift-off method by selective etching. Therefore, the contact layer or both can be formed only on the side surfaces without providing the light absorbing contact layer and / or the electrode on the ridge top and the ridge bottom where light is emitted.

[0015]

Next, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a perspective view of a first embodiment of the semiconductor light emitting device according to the present invention. In the figure, an n-GaAs substrate 1
The n-side electrode 100 made of AuGe is provided on the bottom surface of the substrate 01. On the upper surface of the n-GaAs substrate 101, an n-cladding layer 102, a GaInP active layer 103, a p-cladding layer 1
04 and the contact layer 105 are sequentially formed.

The contact layer 105 has a common electrode portion 1
11 and a plurality of comb-shaped ridges 109 connected thereto, and an electrode 10 is formed on one side of each ridge.
6 are formed, and each of the electrodes 106 is a side electrode 1
13 is connected to the common electrode 111. And
A wire 112 for connection to a terminal (not shown) is bonded to the center of the common electrode 111.

FIG. 2 and FIG. 3 are process sectional views showing the manufacturing process of the first embodiment. In FIG. 2A, first, an n-cladding layer 102 is formed on an n-GaAs substrate 101 by metal organic chemical vapor deposition (MOCVD).
Here, the n-cladding layer is lattice-matched to GaAs (Al
a _{x Ga 1-x) 0.5 In} 0.5 P (x = 0.7). Hereinafter, this quaternary mixed crystal is referred to as AlGaInP (x = 0.7). Ga _0.5 In _0.5 P is referred to as GaInP.

Following the formation of 102, a GaInP active layer 103, an AlGaInP (x = 0.7) p-cladding layer 104, and a p-Al _0.5 Ga _0.5 As contact layer 10
5. An n-GaAs sacrificial layer 107 for lift-off is sequentially formed. Further, an n-side electrode 100 made of AuGe is formed below the GaAs substrate 101 by a vacuum deposition method.

Next, a resist 108 is formed in a comb shape by photolithography (FIG. 2B). FIG.
As shown in (2), a resist is left at the end of the element in order to leave a portion that will later become the common electrode 111 at the end of the element. Then, the sacrifice layer 107 and the contact layer 105 where there is no resist are removed by reactive ion etching (RIE) to form a ridge 109 (FIG. 2).
(C)).

After that, the resist 108 is removed. Next, a p-electrode 106 made of AuZn is formed on the side surface of the ridge and on the sacrificial layer 107 by a vacuum evaporation method. At this time, vapor deposition is performed from an oblique direction. Therefore, as shown in FIG. 3A, the p-electrode 106 is not formed on the light emitting surface 110 which is a shadow of the adjacent ridge, but is formed only on one side surface of the ridge and the upper part of the sacrificial layer 107 on the upper surface of the ridge. You.

Next, only the sacrificial layer 107 is selectively removed by an NH ₄ OH-based etchant. At that time, the electrode on the sacrificial layer is also removed at the same time. FIG. 3B shows the shape of the electrode after the removal. Further, since the electrodes on the side surfaces of the individual ridges are connected to the common electrode portion 111 at the end of the element shown in FIG.
By connecting one wire 112 to 11, current can flow through all ridges. Further, since the common electrode portion 111 has a larger area than the ridge portion, the common electrode portion 111 is not lifted off by the above-mentioned etchant and remains without being removed.

Further, the common electrode portion 111 and the electrodes on the side surfaces of the individual ridges are connected by side electrodes 113. In order to form the 113, the deposition direction at the time of forming the electrodes is as described above. Oblique and side electrode 113
Vacuum deposition is performed in a direction oblique to the surface on which is formed, that is, in a direction perpendicular to the paper surface of FIG. By the method described above, an electrode can be formed only on the side surface of the ridge, and a current can be uniformly applied to the entire surface of the element without hindering light emitted from the active layer immediately below the ridge.

The conductivity type of the sacrifice layer 107 is such that a current blocking function is obtained below the electrode common portion 111.
N, which has a different conductivity type from the contact layer 105 therebelow.
Type. Further, the sacrifice layer 107 may be a high resistance layer.

Here, the present embodiment can be modified as follows. First, the growth method of the semiconductor layers 101 to 107 is not limited to the MOCVD method, but may be a molecular beam epitaxy method (MBE method) or a metalorganic molecular beam epitaxy method (MOM method).
BE method), vapor phase growth method (VPE method), liquid phase growth method (LP
E method) or the like. In this embodiment, the active layer 103 and the cladding layers 102 and 104 form a double hetero structure, but the structure may be a single hetero structure or a homojunction.

The material constituting this embodiment is AlG
The present invention is not limited to aInP and AlGaAs systems, but includes GaAsP, GaP, AlGaN, InGaAsP
III-V compound semiconductors such as ZnCdSSe, Zn
It may be a II-VI compound semiconductor such as CdSeTe or ZnMgSSe, or a chalcopyrite-based semiconductor such as CuAlSSe or CuGaSSe. The substrate is also GaAs
It is not limited to s but may be GaP, InP, sapphire, Si, Ge, or the like.

The etching method for forming the ridge is not limited to the RIE method, but may be any of various wet etching methods. The etching of the sacrificial layer is not limited to the NH ₄ OH-based etchant, and an etchant having selectivity depending on the material system of the sacrificial layer and the contact layer may be used.

Each layer of the light-emitting element shown in this embodiment is basically composed of a GaAs substrate 101 and a cladding layer 1 for improving the crystallinity or electrical characteristics.
02, a GaInP layer buffer layer may be inserted,
In addition, Ga is provided between the cladding layer 104 and the contact layer 105.
An intermediate band gap layer made of a thin layer of InP may be provided.

Next, a second embodiment of the present invention will be described. In the second embodiment, an example is shown in a region where the contact layer absorbs the emission wavelength, aiming at a further shorter emission wavelength than the first embodiment. FIG. 4 is a perspective view of a second embodiment of the semiconductor light emitting device of the present invention. In FIG.
On the bottom surface of the aAs substrate 201, there is a p-side electrode 200 made of AuZn. On the upper surface of the p-GaAs substrate 201,
p-GaInP intermediate band gap layer 202, p-Al
GaInP (x = 0.7) cladding layer 203, AlGa
InP (x = 0.5) active layer 204 and n-AlGaI
An nP (x = 0.7) cladding layer 205 is sequentially formed.

On the n-AlGaInP (x = 0.7) cladding layer 205, a plurality of common electrode portions 111 and a plurality of comb-shaped ridges 209 connected to the common electrode portion 111 are formed. Electrodes 206 are formed,
Each of the electrodes 206 is a common electrode 1 by a side electrode 113.
11 is connected. A wire 112 is bonded to the center of the common electrode 111.

FIGS. 5 and 6 are sectional views in the order of steps showing the manufacturing steps of the second embodiment. Referring to FIG. 5A, first, a molecular beam epitaxy method (M
BE method) and the p-GaInP intermediate band gap layer 202
To form Next, a p-AlGaInP (x = 0.7) cladding layer 203 is formed. Continue with AlGaInP
(X = 0.5) Active layer 204, n-AlGaInP (x
= 0.7) Cladding layer 205, p-Al for lift-off
_{A 0.5} Ga _0.5 As sacrificial layer 208 is sequentially formed. G
The p-side electrode 2 made of AuZn is provided under the aAs substrate 201.
00 is formed by a vacuum evaporation method. The method of forming the ridge 209 is the same as in the first embodiment. Therefore, it is omitted here.

Here, the active layer 204 has an Al mixed crystal ratio of 0.5.
The emission wavelength is as short as about 560 nm. This value is AlA which is the shortest band gap of AlGaAs system.
When the contact layer is formed on the active layer, the emitted light is absorbed.
Therefore, it is impossible to adopt the configuration as in the first embodiment. Therefore, a contact layer is formed by the following method.

After the formation of the ridge, the n-GaAs contact layer 207 is grown by MBE. At this time, as shown in FIG. 5B, a molecular beam of Ga is irradiated from an oblique direction, and growth is performed only on one side surface of the ridge 209 and the upper surface of the sacrificial layer 208. Here, the contact layer 207 does not grow on the light emitting surface 210 because it becomes a shadow of the adjacent ridge.

Next, an n-electrode 206 made of AuGe is formed on the contact layer 207 by a vacuum deposition method. At this time, the vapor deposition is performed in an oblique direction as in the first embodiment. Therefore, as shown in FIG. 6A, the n-side electrode 206 is not formed on the light emitting surface 210 which is a shadow of the adjacent ridge.

Next, only the sacrificial layer 208 is selectively removed by an etchant of H ₂ SO ₄ . At that time, the sacrificial layer 20
The upper contact layer 207 and the electrode 206 are also removed by lift-off. Figure 6 shows the shape of the ridge after removal.
This is shown in FIG.

According to the above-described method, the contact layer and the electrode can be formed only on the side surfaces of the ridge, and the current can be uniformly supplied to the entire surface of the element without obstructing the light emitted from the active layer immediately below the ridge. Become. In particular, this embodiment is effective when direct ohmic connection between the cladding layer and the electrode is difficult and the contact layer involves light absorption. This embodiment can be modified in the same manner as the items shown in the first embodiment. However, regarding the growth of the contact layer, it is necessary to use a crystal growth method having a directionality such as the MBE method.

[0036]

As described above, according to the present invention, there is provided an electrode structure capable of injecting current into a semiconductor light emitting device uniformly over the entire surface of the device and without blocking light from a light emitting layer. can do. Thereby, light generated in the light emitting layer is extracted to the upper surface of the element without loss, and there is an effect that the external emission efficiency of the light emitting element is increased. In particular, it is effective for a system that requires a contact layer that is not transparent to the emission wavelength.
This is effective for increasing the luminance and shortening the wavelength of a P-based light emitting element. Ma
Under the common electrode, there is a different kind of conductive
By providing a semiconductor layer with high resistance or high resistance,
Blocks the current underneath and emits light in the active layer under the common electrode.
And improve luminous efficiency.

For the bottom of the ridge from which light exits,
Since the formation of the electrode or the contact layer is not formed from the beginning by utilizing the shadow of the adjacent ridge, there is an effect that the electrode can be easily formed only on the side surface of the ridge. Ridge upper surface
The sacrificial layer for removing the electrode formed in
Since it also serves as a conductor layer, the manufacturing process is simplified.

[Brief description of the drawings]

FIG. 1 is a perspective view of a first embodiment of a semiconductor light emitting device according to the present invention.

FIG. 2 is a first half of a process order sectional view of the first embodiment of the semiconductor light emitting device according to the present invention.

FIG. 3 is a second half of a process order sectional view of the first embodiment of the semiconductor light emitting device according to the present invention;

FIG. 4 is a perspective view of a second embodiment of the semiconductor light emitting device according to the present invention.

FIG. 5 is a first half of a process order sectional view of a second embodiment of the semiconductor light emitting device according to the present invention.

FIG. 6 is a second half of a process order sectional view of a second embodiment of the semiconductor light emitting device according to the present invention.

FIG. 7 shows a conventional example.

FIG. 8 shows a conventional example.

FIG. 9 shows a conventional example.

[Explanation of symbols]

Reference Signs List 100 n-side electrode 101 n-GaAs substrate 102 n-AlGaInP (x = 0.7) cladding layer 103 GaInP active layer 104 p-AlGaInP (x = 0.7) cladding layer 105 p-Al _0.5 Ga _0.5 As contact layer 106 p-side electrode 107 n-GaAs sacrifice layer 108 resist 109 ridge 110 light emitting surface 111 common electrode portion 112 wire 200 p-side electrode 201 p-GaAs substrate 202 p-GaInP intermediate band gap layer 203 p-AlGaInP (x = 0.7 ) Cladding layer 204 AlGaInP (x = 0.5) active layer 205 n-AlGaInP (x = 0.7) cladding layer 206 n-side electrode 207 n-GaAs contact layer 208 p-sacrifice layer (Al _0.5 Ga _0.5 As) 209 Ridge 210 Light emitting surface 1001 Side electrode 1002 n-GaAs substrate 1003 n-AlGaInP cladding layer 1004 GaInP active layer 1005 p-AlGaInP cladding layer 1006 p-GaAs contact layer 1007 p-side electrode 1009 current diffusion layer 1010 comb-shaped electrode 1011 p-GaAs contact layer 1020 injection Current

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int. Cl. ⁷ , DB name) H01L 33/00

Claims (7)

(57) [Claims] 1. A semiconductor device comprising: a clad layer, an active layer,
In the semiconductor light emitting device where the cladding layer are sequentially formed, to form a ridge on the top of elements is a light emitting surface, the element top surface
The semiconductor light emitting device characterized substantially to the formation of the electrode only on the side surface perpendicular the ridge to. 2. The semiconductor light emitting device according to claim 1, further comprising a contact layer between the side surface and the electrode. 3. The device according to claim 1, wherein a plurality of ridges formed on the light emitting surface are connected to each other, and a common electrode connected to the side electrode is formed on a part of the upper surface of the device. A semiconductor light emitting device characterized by the above-mentioned. 4. A semiconductor device comprising : a clad layer, an active layer,
In a semiconductor light emitting device in which a cladding layer is sequentially formed, a ridge is formed on the upper surface of the device, which is a light emitting surface, and the active layer is
In order not to block the emitted light, at least the ridge
Also, an electrode is formed on one side, and a plurality of ridges formed on the light exit surface are connected and formed.
And a common electrode connected to the side electrode is provided on the upper surface of the device.
And a semiconductor layer of a different conductivity type or high resistance from a layer adjacent to the lower layer is provided below the common electrode. 5. The method according to claim 4, wherein a core is provided between the side surface and the electrode.
Semiconductor light emitting device comprising a contact layer
Child. On at least one side of 6. ridges formed by a plurality linked, in the manufacturing method of forming a contact layer or electrode, or both, as next contact ridge serves as a mask, the semiconductor light emitting element Inject material obliquely to the surface of the ridge and deposit the contact layer and / or electrodes on the sides of the ridge.
A method for manufacturing a semiconductor light emitting device, comprising a step of stacking and forming . 7. A small number of ridges formed by connecting a plurality of ridges.
In a manufacturing method in which an electrode is formed on at least one side surface, a clad layer, an active layer, and a clad layer are sequentially formed on a semiconductor substrate.
A next forming step, and further different types of conductive types or
Forming a semiconductor layer of high resistance as sacrificial layer, as the adjacent ridge serves as a mask, the semiconductor light emitting element
Inject material from the diagonal direction to the surface of the
An electrode is formed on the side surface, and a common electrode connected to the side electrode is
Forming a part of the upper surface of the element and removing only the sacrificial layer of the ridge by selective etching
A method of manufacturing a semiconductor light emitting device.