JP2856374B2 - 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 and a method for manufacturing the same, and more particularly, to a light emitting diode using a compound semiconductor material, a semiconductor light emitting device such as a semiconductor material, and a method for manufacturing the same.

[0002]

2. Description of the Related Art Light emitting diodes (hereinafter, referred to as LEDs) have high reliability and are used in various display devices as light sources instead of tungsten lamps, and have been spotlighted as indoor and outdoor display devices. With the increase in brightness of LEDs, in particular, the outdoor display market is expected to accelerate in the next few years, and is expected to grow into a medium that will become a neon sign in the future. The high-brightness LED has been realized for several years as a GaAlAs-based red LED having a DH (double hetero) structure.

An In _1-y (Ga _1-x Al _x ) _y P mixed crystal semiconductor (0 ≦ x ≦ 1, 0 ≦ y ≦ 1) is a direct transition among III-V group compound semiconductors lattice-matched to GaAs. Since it has the largest band gap in the region, it is attracting attention as a light emitting element material in the visible light region. The LED in the visible light region is GaAlAs in the red light region (wavelength 630 to 660 nm).
A high-brightness LED is obtained by the use of an InGaAlP-based mixed crystal in a shorter wavelength region.
Promising for ED.

In order to obtain an LED with high quantum efficiency, it is necessary to inject carriers into the active layer over the entire chip. To achieve this, the series resistance of the LED must be reduced and the injected carriers must be sufficiently diffused in the upper cladding layer. However, the low resistivity InGaAlP
Getting it is not easy. In an InGaAlP material, only a part is activated even if a p-type impurity is added at a high concentration, and the electron mobility is 100 cm ² / Vse in a γ-type impurity.
c and low. Therefore, most of the light-emitting recombination in the active layer occurs immediately below the upper electrode because the injected current is unlikely to spread in the lateral direction. Light emission is observed only in the periphery of the upper electrode, and the light extraction efficiency is extremely poor. Therefore,
Conventionally, the following structure has been considered.

FIG. 7 shows an example of a conventional semiconductor light emitting device. The LED 100 includes a GaAs buffer layer 119, an n-InGaAlP cladding layer 112, an InGaAlP active layer 113, and a p-I
An nGaAlP cladding layer 114, a p-InGaAlP current spreading layer 115, and a p-InGaAlP ohmic contact layer 116 are grown in this order.

The upper electrode 117 is formed on the p-GaAs ohmic contact layer 116, and the lower electrode 118 is formed on the lower surface of the n-GaAs substrate 111. Further, p-InGa corresponding to a portion directly below the upper electrode 117 is used.
A current blocking layer 119 is formed on the AlP cladding layer 114.

In this LED 100, the current blocking layer 119
Is p-In to suppress light emission from the active layer immediately below the upper electrode 117 and to diffuse carriers throughout the chip.
The GaAlP current diffusion layer 115 is regrown to improve the light extraction efficiency.

FIG. 8 shows another example of a conventional semiconductor light emitting device. In the LED 100, an intermediate energy gap layer 120 is selectively formed below the n-InGaAlP cladding layer 112 so as to have a pattern opposite to the pattern of the upper electrode 117. Thereby, the upper electrode 117
The light extraction efficiency is improved by reducing the voltage drop in the portion where the intermediate energy gap layer 120 is present in the vicinity of and by passing a current outside the upper electrode 117.

[0009]

As described above, the conventional LE
D100 is designed so that the upper electrode 117 does not block the radiated light, but has the disadvantage that it must be grown twice because it selectively grows the current blocking layer 119 and the intermediate energy gap layer 120. is there.

In the case of the first conventional example, after the current blocking layer 119 is grown during the first growth, selective etching is performed on portions other than the portion where the upper electrode 117 is to be formed, and then Al
With the difficulty of regrowth on mixed crystals containing p-InG
A recombination level is generated at the interface between the aAlP cladding layer 114 and the p-InGaAlP current diffusion layer 115. For this reason, non-radiative recombination of carriers occurs, and p-InGaAlP
The crystallinity of the current diffusion layer 115 is reduced, which causes the resistivity to be further increased.

In the second embodiment, the intermediate energy gap layer 120 is grown after the n-GaAs substrate 111 is mesa-etched, and only the upper part of the mesa must be etched again to make it flat. In either case, the growth is performed twice, which complicates the process and increases the growth time. For this reason, the cost becomes high, and there is a great obstacle in terms of productivity.

The present invention has been made to improve the above-mentioned conventional disadvantages, and has as its object to diffuse carriers throughout the device without flowing carriers into the active layer immediately below the upper electrode. The current blocking layer is selectively formed during one epitaxial growth, thereby simplifying the process, improving productivity, and manufacturing at a low cost. Another object of the present invention is to improve the crystallinity by reducing the recrystallization level to increase the luminous efficiency, to prevent the formation of a high-resistance layer, and to improve the characteristics of the light-emitting diode.

[0013]

According to the present invention, there is provided a semiconductor light emitting device comprising: a light emitting layer formed by pn junction on a substrate; a current passing portion which is selectively photoexcited from the outside and inverted to p-type;
And a current selection layer in which an n-type current blocking portion that is not photoexcited immediately below the upper electrode is stacked on the light emitting layer, and a current diffusion layer that injects a current stacked on the current selection layer,
The above object is achieved.

According to the method of manufacturing a semiconductor light emitting device of the present invention, there are provided a step of forming a light emitting layer by pn junction on a substrate; Laminating a current selection layer having an n-type current blocking portion that is not photoexcited immediately below the light-emitting layer, and laminating a current diffusion layer for injecting a current on the current selection layer. , Whereby the above object is achieved.

[0015]

According to the present invention, the pn inversion is caused by selectively irradiating light from the outside during the growth of the current selection layer, and only the region irradiated with light is inverted to the p-type to thereby make the current passing portion. Is formed, and a current blocking portion is formed by holding a region not irradiated with light as it is in the n-type. Since the current blocking portion is formed in the chip, the step of selectively etching after growing once and then forming the current diffusion layer is omitted. Therefore, the process is simplified, the productivity is improved, and the device is manufactured at low cost.

Further, by improving the crystallinity by reducing the recrystallization level, the luminous efficiency is increased, the formation of a high resistance layer is prevented, and the characteristics of the light emitting diode are improved. This prevents recombination levels from regenerating at the interface between the upper cladding layer and the current diffusion layer, and prevents deterioration in characteristics such as deterioration in crystallinity due to regrowth.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the semiconductor light emitting device of the present invention will be described below with reference to the drawings. FIG. 1 shows a first example of the semiconductor light emitting device of the present invention.
An example will be described.

The LED 10 of this structure is an n-GaAs substrate 1
1, an n-GaAs buffer layer 19, n-InGa
AlP cladding layer 12, InGaAlP active layer 13, p
-InGaAlP cladding layer 14, current selection layer 20, p
The -InGaAlP current diffusion layer 15 and the p-InGaP ohmic contact layer 16 are stacked in this order. The upper electrode 17 is stacked on the upper surface of the p-InGaAlP ohmic contact layer 16, and the lower electrode 18 is formed of n-GaAs.
It is stacked on the lower surface of the substrate 11. The upper electrode 17 is formed at the center as shown in the figure.

The LED 10 of this structure has a current blocking portion 20a formed immediately below the upper electrode 17, and a current selection layer 2 formed with a current passing portion 20b other than immediately below the upper electrode 17.
Has zero.

Each layer of the LED 10 has the following composition. The n-GaAs substrate 11 has an n concentration of 5 × 10 ¹⁸ cm ⁻³ by Si doping. n-GaAs
The s buffer layer 19 has an n concentration of 2 × 10
¹⁹ cm ^-3 . The n-InGaAlP cladding layer 12 has an n concentration of 2 × 10 ¹⁹ cm ⁻² by Si doping, and a layer thickness of 2 × 10 ¹⁹ cm ⁻² .
μm. The InGaAlP active layer 13 is composed of In _0.51 (G
a _0.55 Al _0.45 ) _0.49 P clad layer, undoped and 0.5 μm thick. The p-InGaAlP cladding layer 14 is a p-In _0.51 (Ga _0.3 Al _0.7 ) _0.49 P cladding layer 14 having a p concentration of 4 × 10 ¹⁷ c by Zn doping.
m ⁻³ , the layer thickness is 1 μm. The p-InGaAlP current diffusion layer 15 has a configuration of the p-In _0.51 (Ga _0.3 Al _0.7 ) _0.49 P current diffusion layer 15, and the p concentration by Zn doping = 7 × 1
0 ¹⁷ cm ^-3 and a layer thickness of 1 μm. The p-InGaP ohmic contact layer 16 has a configuration of a p-In _0.31 Ga _0.49 P ohmic contact layer 16 and is formed by p-doping with Zn.
The concentration = 1 × 10 ¹⁹ cm ⁻³ , and the layer thickness is 0.05 μm.

Each layer of the LED 10 has the above composition. The LED 10 has a lower clad layer 12, an active layer 13, and an upper clad layer 14 sequentially formed on a substrate 11, and is called a DH (double hetero) structure. The current selection layer 20 in the stack by selectively photoexcited during the epitaxial growth, n-In _{0. 51}
(Ga _0.3 Al _0.7 ) _0.49 P current blocking portion 20a and p-I
_{n 0.51 (Ga 0.3 Al 0 .7} ) to form a _0.49 P current passing portion 20b.

Next, an embodiment of the method for manufacturing a semiconductor light emitting device of the present invention will be described. 2A to 2D are cross-sectional views schematically showing the manufacturing process. First, as shown in FIG. 2A, n-concentration by Si doping = 5 × 10 ¹⁸ cm ⁻³ n-
On a GaAs substrate 11, Si is deposited by MOCVD.
R concentration of dope = 2 × 10 ¹⁹ cm ⁻³ , layer thickness 0.3 μm
The n-GaAs buffer layer 19 is grown. And
N-In _0.51 (Ga _0.3 Al _0.7 ) _0.49 P cladding layer 12 having an n concentration of 5 × 10 ¹⁹ cm ⁻² and a thickness of 2 μm due to Si doping, and an In-doping layer having a thickness of 0.5 μm
_0.51 (Ga _0.3 Al _0.7 ) _0.49 P active layer 13, Zn-doped p-concentration = 4 × 10 ¹⁷ cm ^-3 , layer thickness 1 μm p-I
n _0.51 (Ga _0.3 Al _0.7 ) _0.49 P The first cladding layer 14 is grown in this order.

In manufacturing the LED 10, a photo-excitation type M
An OCVD apparatus is used. FIG. 3 shows the configuration of a photo-excitation type MOCVD apparatus. The photoexcitation type MOCVD apparatus 30 includes a box-shaped reactor 31 made of quartz, a flow channel 32 housed in the reactor 31, and a top surface protruding from the lateral direction inside the reactor 31 and inside the flow channel 32. And a susceptor 33 made of carbon having an exposed portion. A high-frequency coil 34 is wound around an outer peripheral wall of the reactor 31, a light introducing hole 31 a is formed at an upper portion of the outer peripheral wall, and gas introducing holes 36, 37, and 38 are provided at a side wall 35. Above the reactor 31, an excitation laser 41 and a mirror 4 are provided.
2. A selective excitation mask 43, an optical system 44 and the like are arranged.

The n-GaAs substrate 11 is placed on a susceptor 33, which is heated to a predetermined temperature by a high-frequency coil 34. In the reactor 31, the gas inlet 3
Group III organic metal gas and group V halide gas are introduced from 6 and 37 and flow into the flow channel 32. From the gas inlet 38, a carrier gas H2 is introduced, flows outside the flow channel 32, and prevents reaction products from adhering to the inner wall of the reactor 31.

The MOCVD apparatus 30 is of a photo-excitation type.
Light introduction hole 31a through which cooling water does not flow on the upper wall of reactor 31
Is formed on the upper wall of the flow channel 32.
2a is formed. The excitation light is emitted from the excitation laser 41 by reflecting the 193 nm laser light (ArF excimer laser) on the mirror 42 and irradiating the n-GaAs substrate 11. The mask 4 for selective excitation is provided on the n-GaAs substrate 11.
(3) Light is irradiated spatially selectively using the optical system 44.

The principle of the pn inversion of the growth layer by the excitation light is as follows. FIG. 4 shows V vs. impurity carrier concentration.
4 shows the dependence of the / III ratio. Group III raw materials are trimethyl indium (TMI), trimethyl gallium (TMA), and trimethyl aluminum (TMA), and group V raw materials are phosphine (PH3). In the growth of InGaAlP, the introduction of n-type impurity Si is promoted as the V / III ratio increases, so that the conduction type is switched from p-type to n-type. Now, when photoexcited from the outside, the decomposition of PH3 is promoted, and the effective V / III ratio on the growth surface is increased, or the decomposition of n-type impurities is promoted. When the rate of incorporation of Si into the crystal increases, an inversion position is supplied from the non-irradiated portion indicated by the dotted line to the light-irradiated portion indicated by the solid line in FIG.
/ III ratio.

According to an experiment, when the film is grown while irradiating light using the MOCVD apparatus 30 shown in FIG. 3, the V / III ratio (100) indicated by the arrow shown in FIG. It was found that the portion not irradiated with light became p-type.

Therefore, as shown in FIG.
As shown in FIG. 2B, only a portion corresponding to a portion immediately below the upper electrode 17 which is to be laminated later is irradiated with light to be photo-excited, and n-In _0.51 (Ga _0.3 Al _0.7 ) _{0.49 is formed.}
The P current blocking section 20a is manufactured. In a portion not irradiated with light, the light becomes p-type at the set V / III ratio, and p-I
n _0.51 (Ga _0.3 Al _0.7 ) _0.49 It becomes the P current passage portion 20b.

Next, as shown in FIG. 2C, a p-In _0.51 (Ga _0.3 Al _0.7 ) _0.49 P current diffusion layer 15 is grown by Zn doping, and the epitaxial growth is completed. After the upper electrode 17 and the lower electrode 18 are formed by evaporation, the p-InGaAlP ohmic contact layer 16 and the upper electrode 17, which are the upper portions of the current blocking portions 20a, are removed, and then removed by etching. According to such a manufacturing method,
Current blocking portion 20 by etching after double hetero growth
After forming a, it is not necessary to take the twice growth process of growing the current diffusion layer 15 again. Therefore, generation of recombination levels on the regrown surface can be suppressed, and crystallinity is also improved. Further, the process can be simplified, and the resistance of the LED 10 can be reduced.

As a result of the experiment, the characteristic that the epi-substrate having undergone the above-mentioned steps was made into a device of 300 μm square was a peak wavelength of 550 nm.
m green emission was observed from around the upper electrode 17. When this LED 10 was resin-molded into a 5 mmφ lamp and measured for luminance, a luminance of 3000 mcd was obtained at a forward current of 20 mA.

FIG. 5 shows a second embodiment of the semiconductor light emitting device of the present invention. The LED 10 of this structure is the LED 10 of the first embodiment.
And the structure is almost the same. The difference from the LED 10 of the first embodiment is that the patterns of the current blocking portion 20a and the current passing portion 20b are reversed. In the first embodiment, the current blocking portion 20a is formed in the center, and the current passing portion 2a is formed.
0b is formed on the outside. On the other hand, in the second embodiment, the current blocking portion 20a is formed outside and the current passing portion 20b is formed in the center.

Accordingly, the upper electrode 17 and the p-InG
The shape of the aAlP ohmic contact layer 16 is also formed opposite to that of the first embodiment. Therefore, the upper electrode 1
The current emitted from 7 passes through the central current passing portion 20b in a concentrated manner as shown in FIG. 5, and flows to the n-GaAs substrate 11. Therefore, according to the LED 10 of the second embodiment, the current density in the light emitting region can be made higher than that of the first embodiment, and the LED 10 of higher luminance can be provided.

FIG. 6 shows a third embodiment of the semiconductor light emitting device of the present invention. The LED 10 having this structure is a current selection layer 2 for photoexcitation.
0 is formed below the InGaAlP active layer 13.
Since the LED 10 has the current selection layer 20 provided before the growth of the InGaAlP active layer 13, the LED 10 has a double hetero structure without exposing the pn junction to high temperatures for a long time. As a result, diffusion of impurities is reduced, and crystallinity can be improved. The characteristic of the LED 10 having this structure is 5
When a resin mold of mmφ was mounted, a luminance of 3500 mcd was obtained when the forward current was 20 mA.

Although the shape and pattern of the upper electrode 17 are not particularly described in the embodiment of the semiconductor light emitting device of the present invention, the shape and pattern of the upper electrode 17 are not necessarily limited to a simple one such as a circle or a square. The shape and pattern of the upper electrode 17 may be any patterns that allow the injected carriers to be efficiently diffused.
It is desirable that the pattern of the upper electrode 17 and the pattern of light excitation for forming the current blocking portion 20a match.

In this embodiment, the composition of the current selection layer 20 is In _0.51 (Ga _0.3 Al _0.7 ) _0.49 P.
It is desirable to have a band gap sufficient to be transparent to the emission wavelength from the GaAlP active layer 13. In the embodiment, the composition of the InGaAlP active layer 13 is In _0.51 (Ga _0.3 Al _0.7 ) _0.49 P.
The emission wavelength from red to green can be obtained by changing the Al composition. The composition of the cladding layer desirably has a sufficient difference in band gap to confine carriers. The current diffusion layer 15 only needs to be transparent to the emission wavelength, and may be a GaAlAs layer. In this embodiment, Si is used as the dopant of the current selection layer 20, but the same effect can be obtained by using an n-type impurity such as Se or S.

[0036]

According to the present invention, in a light emitting material using an InGaAlP-based material, a current blocking portion for diffusing carriers in a p-type cladding layer is formed by pn inversion due to photoexcitation. The step of selectively etching after growing the current once and the step of re-growing the current diffusion layer are omitted as in the prior art, so that the productivity is improved and the cost is reduced.

Also, since there is no regrowth interface having a high Al mixed crystal ratio, the recrystallization level is reduced, the crystallinity is improved, the luminous efficiency is increased, the formation of a high resistance layer is prevented, and the characteristics of the light emitting diode are reduced. Is improved. This prevents recombination levels from regenerating at the interface between the upper cladding layer and the current diffusion layer, and prevents deterioration in characteristics such as deterioration in crystallinity due to regrowth. by this,
Since the LED can efficiently extract light to the outside and improve the crystallinity and prevent the formation of a high-resistance layer, the characteristics of the light-emitting diode can be improved.

[Brief description of the drawings]

FIG. 1 is a schematic view showing an embodiment of the structure of the semiconductor light emitting device of the present invention.

FIG. 2 is a schematic view showing a manufacturing process of the semiconductor light emitting device of the present invention.

FIG. 3 is a photo-excitation type MO for manufacturing the semiconductor light emitting device of the present invention.
Sectional drawing which shows a CVD growth apparatus.

FIG. 4 is a diagram showing the V / III ratio dependency of the impurity carrier concentration.

FIG. 5 is a sectional view showing a second embodiment of the semiconductor light emitting device of the present invention.

FIG. 6 is a sectional view showing a third embodiment of the semiconductor light emitting device of the present invention.

FIG. 7 is a sectional view showing an example of a conventional semiconductor light emitting device.

FIG. 8 is a sectional view showing another example of a conventional semiconductor light emitting device.

[Explanation of symbols]

 10, LED 11, n-GaAs substrate 12, n-InGaAlP clad layer 13, InGaAlP active layer 14, p-InGaAlP clad layer 15, p-InGaAlP current diffusion layer 16, p-InGaAlP ohmic contact layer 17, upper electrode 18, Lower electrode 19, n-GaAs buffer layer 20, current selection layer 20a, current blocking section 20b, current passing section

Continuation of the front page (72) Inventor Saburo Yamamoto 22-22 Nagaikecho, Abeno-ku, Osaka-shi, Osaka Inside Sharp Corporation (56) References JP-A-3-89568 (JP, A) JP-A-1-120085 (JP JP-A-63-36588 (JP, A) JP-A-62-145888 (JP, A) (58) Fields studied (Int. Cl. ⁶ , DB name) H01L 33/00

Claims (7)

(57) [Claims] 1. A substrate having a first region and a second region.
A light-emitting layer above, a p-type cladding layer, and a light-emitting layer positioned outside the p-type cladding layer.
A p-type current passing portion provided in the first region;
Current selection including n-type current blocking portion provided in second region
The current is emitted by the n-type current blocking portion.
Current selection layer directed to a portion of the layer corresponding to the first region
And a III-V compound semiconductor light-emitting diode comprising:
The n-type current blocking section includes the current selection section including the p-type current passing section.
In the process of growing the selective layer, the group V raw material / the group III raw material
Is set to a predetermined value, and the laser light is applied to the substrate.
A semiconductor light emitting diode formed by irradiating the second region . 2. The III-V group compound is InGaAl.
2. The semiconductor light emitting diode according to claim 1, comprising P. 3. The semiconductor light-emitting diode is a surface-emitting type.
And further comprising a current spreading layer.
3. The semiconductor light emitting diode according to 2. 4. A substrate having a first area and a second area.
A light-emitting layer above the a p-type cladding layer; The light emitting layer is located outside the p-type cladding layer.
A p-type current passing portion provided in the first region;
Current selection including n-type current blocking portion provided in second region
The current is emitted by the n-type current blocking portion.
Current selection layer directed to a portion of the layer corresponding to the first region
When, Of group III-V compound semiconductor light emitting diode provided with
The method The n-type current blocking section is connected to the current selection section including the p-type current passing section.
In the process of growing the selective layer, the group V raw material / the group III raw material
Is set to a predetermined value, and the laser light is applied to the substrate.
A semiconductor formed by irradiating the second region of
Manufacturing method of body light emitting diode. 5. The method according to claim 1, wherein the step of growing the n-type current blocking portion is performed.
In the irradiation of the laser light, the substrate of the
Group V raw material / Group III raw material ratio near the second region Improved
Wherein the decomposition of the n-type impurities is promoted.
5. The method for manufacturing a semiconductor light emitting diode according to item 4. 6. The group III-V compound is InGaAl.
6. The semiconductor light emitting diode according to claim 4, which contains P.
Manufacturing method. 7. The semiconductor light emitting diode is a surface emitting type.
And further comprising a current spreading layer.
6. A method for manufacturing a semiconductor light-emitting diode according to any one of 6.
Law.