JPH04241475A - Epitaxial wafer - Google Patents

Abstract

PURPOSE:To provide a novel AlGaAs epitaxial wafer used for manufacturing a high output infrared ray emitting diode to be used as a light emitting source of a photo coupler, an infrared ray remote controller, etc. CONSTITUTION:An epitaxial wafer comprises n-type AlxGa1-xAs (0.01<=x<=0.4) with Si added, p-type AlyGa1-yAs (0<y<=0.05) with Si added and p-type AlzGa1-zAS (0.1<=z<=0.3) as thick as 5mum to 30mum, which are laminated in this sequence. Use of the invented epitaxial wafer allows a light emission diode which emits light of short wavelength of 940nm or less with high efficiency to be obtained easily.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] This invention is an Aluminum light emitting diode used in the manufacture of high output infrared light emitting diodes used as light sources for photocouplers, infrared remote controllers, etc.
This invention relates to GaAs epitaxial wafers.

0002

2. Description of the Related Art Epitaxial wafers for high-output infrared light emitting diodes have conventionally had a cross-sectional structure as shown in FIG. In FIG. 2, n-type GaA
An n-type GaAs epitaxial layer 6 doped with Si and a p-type GaAs epitaxial layer 5 doped with Si are laminated on the s-substrate 7, and a p-type AlGaAs epitaxial layer 4 doped with Si is further provided thereon. There is. (For example, Japanese Patent Application Laid-open No. 171116/1983)

000
3] In this conventional epitaxial wafer, p
The type AlGaAs epitaxial layer 4 is said to have the following functions. That is, since a heterojunction potential barrier exists at the interface between the p-type AlGaAs epitaxial layer 4 and the p-type GaAs epitaxial layer 5,
Electrons injected into the p-type GaAs epitaxial layer 5 effectively contribute to light emission. Also, for the generated light, p-type A
Since the lGaAs epitaxial layer 4 is transparent, light can be effectively extracted to the outside. As a result, the luminous efficiency is increased as a whole, and a high-output infrared light emitting diode can be obtained.

0004

However, in the conventional epitaxial wafer for infrared light emitting diodes described above, since the materials of the light emitting region are the n-type GaAs epitaxial layer 6 and the p-type GaAs epitaxial layer 5, the wavelength of the light is It was limited to a range of about 950 to 960 nm. If shorter wavelengths are required, the light emitting region can be replaced with AlGaA
It is well known that if the wavelength is changed to s, it is possible to emit light with a wavelength of 940 nm or less. However, when the wavelength is shortened in this way, the light emitted from the light emitting region made of AlGaAs and directed toward the n-type GaAs substrate 7 is
It is absorbed in the As substrate 7. Therefore, the overall luminous efficiency is lower than that of a diode having a GaAs light emitting region, and it has been difficult to obtain an infrared light emitting diode that has a high output at a short wavelength.

An object of the present invention is to solve the problems of the prior art as described above and to provide an epitaxial wafer for a high-output infrared light emitting diode having a light emitting region made of AlGaAs.

[0006]

[Means for Solving the Problems] The epitaxial wafer of the present invention has Si-doped n-type AlxGa1-xA
s, p-type AlyGa1-yAs added with Si, and S
p-type Al with a thickness of 5 μm to 30 μm doped with i
It is characterized in that zGa1-zAs are stacked in this order.

[0007]

[Function] The epitaxial wafer of the present invention has a light emitting region of n-type AlxGa1-xAs and p-type AlyGa1.
-yAs, by appropriately selecting the Al composition ratios x and y, it is possible to obtain an emission wavelength in the range of 860 nm to 940 nm. In addition, since p-type AlzGa1-zAs is stacked on top of this light emitting region, a potential barrier due to the difference in Al composition between the p-type AlzGa1-zAs layer and the p-type AlyGa1-yAs layer
Electrons injected into the light emitting region do not diffuse outside the light emitting region and effectively contribute to light emission. That is, the epitaxial wafer of the present invention as a whole has a function of generating light with a short wavelength of 940 nm or less with high efficiency.

[0008]

[Embodiment] Figure 1 shows the first embodiment of the present invention.
1 schematically shows a cross-sectional structure of a GaAs epitaxial wafer. N-type AlxGa1-xAs with a thickness of 150 μm and added with Si of 1x1017 cm-3 or more
Layer 1 (at the surface, x=0.1) and 1×10 Si
P-type A with a thickness of 150 μm with addition of 18 cm −3 or more
lyGa1-yAs layer 2 (at the pn interface, y=0.
01) and Si added at 1×1018 cm−3 or more,
p-type AlzGa1-zAs layer 3 with a thickness of 10 μm (z=0.3 at the interface with p-type AlyGa1-yAs)
and were laminated as shown in Figure 1.

Each epitaxial layer is made of Si-doped n-type GaAs using a normal liquid phase epitaxial growth method.
n-type AlxGa1-xA on a substrate (not shown)
s layer 1, p-type AlyGa1-yAs layer 2, and p-type A
The lzGa1-zAs layer 3 was grown, and then only the substrate was removed by a known selective etching technique.

A light emitting diode was fabricated using this AlGaAs epitaxial wafer. Dot-shaped electrodes are formed on both sides of the wafer, and the light output is changed to n-type AlxGa1.
-xThe structure was such that the As layer 1 was taken out from the surface side. The characteristics of the obtained light-emitting diode are that the light emission wavelength is 940 nm, and the light output is 1.5 nm on average compared to the light-emitting diode manufactured from the epitaxial wafer with the conventional structure shown in FIG.
It was four times as large.

Next, a second embodiment of the invention will be described. The AlGaAs epitaxial wafer of the second embodiment has a cross-sectional structure as shown in FIG. 1, the same as that of the first embodiment. N-type AlxGa1-xAs with a thickness of 80 μm and added with Si of 1x1017 cm-3 or more
Layer 1 (at the surface, x=0.35) and Si 1×1
p-type AlyGa1-yAs layer 2 with a thickness of 180 μm (p-type AlzGa1-zAs
At the interface with layer 3, y=0.01) and Si 1×
A p-type AlzGa1-zAs layer 3 with a thickness of 10 μm (p-type AlyGa1-yAs
z=0.3) were laminated as shown in FIG. The wafer manufacturing method is the same as in the first embodiment.

A light emitting diode was fabricated using this AlGaAs epitaxial wafer. Dot-shaped electrodes are formed on both sides of the wafer, and the light output is changed to n-type AlxGa1.
-xThe structure was such that the As layer 1 was taken out from the surface side. The characteristics of the obtained light-emitting diode were that the light emission wavelength was 880 nm, and the light output was 1.5 nm on average compared to the light-emitting diode manufactured from the epitaxial wafer with the conventional structure shown in FIG.
It was three times as much.

The thickness of each epitaxial layer, the Al composition x and the amount of Si added are not limited to the values of the first and second embodiments. It is appropriate that the thickness of the n-type AlxGa1-xAs layer 1 is 80 to 220 μm. If it is thinner than 80 μm, holes injected from the pn junction will
Since it diffuses to the surface of the xGa1-xAs layer 1 and causes surface recombination, the light emission output decreases. If it is thicker than 220 .mu.m, light absorption increases and light emission output decreases, and epitaxial growth takes a long time, making it impractical. A
The l composition x is 0 in the depth range of 5 μm from the surface.
．． A value of 01 or more and 0.4 or less is appropriate. If it is less than 0.01, light absorption becomes large and high output cannot be obtained. If it exceeds 0.4, the contact resistance of the electrode will increase, and the forward voltage drop of the light emitting diode will increase. The amount of Si added is 1×1
017 cm-3 or more is suitable. 1×1017cm-
If it is less than 3, the luminous efficiency will be low and the series resistance of the light emitting diode will be large.

The thickness of the p-type AlyGa1-yAs layer 2 is 2
A suitable range is 0 to 220 μm. If it is thinner than 20 μm, electrons injected from the pn junction do not effectively contribute to radiative recombination, resulting in a decrease in light emission output. 220μ
If it is thicker than m, the absorption of light increases, the light emission output decreases, and epitaxial growth takes a long time, which is not practical. The Al composition y in the vicinity of the interface with the p-type AlzGa1-zAs layer 3 is suitably 0.4 or less. y=
When the value is 0, light absorption increases and high output cannot be obtained. If it exceeds 0.4, the series resistance of the light emitting diode will increase. Here, the term "near the interface" refers to the range up to 5 μm from the geometric interface. The amount of Si added is suitably 1×10 18 cm −3 or more. If it is less than 1×10 18 cm −3 , the luminous efficiency will be low and the series resistance of the light emitting diode will be large.

The thickness of the p-type AlzGa1-zAs layer 3 is 5
It is appropriate to set it to 0-30 micrometers. If it is thinner than 5 μm, it will be difficult to ensure thickness uniformity during epitaxial growth. If it is thicker than 30 μm, light absorption increases and light emission output decreases. It also takes a long time to grow. The Al composition z in the vicinity of the interface with the p-type AlyGa1-yAs layer 2 is suitably 0.1 or more and 0.3 or less. If it is less than 0.1, light absorption becomes large and high output cannot be obtained. The meaning of ``near the interface'' is the same as above. 0.
If it exceeds 3, the series resistance of the light emitting diode becomes large. The amount of Si added is suitably 1×10 18 cm −3 or more. If it is less than 1×10 18 cm −3 , the series resistance of the light emitting diode becomes large.

In the above embodiment, n-type AlxGa
The 1-xAs layer 1 and the p-type AlyGa1-yAs layer 2 are:
Continuous growth was performed using the vertical dipping method from the same raw material solution. However, the method is not limited to this, and each epitaxial layer can also be grown sequentially using a slide boat. However, the number of wafers that can be grown simultaneously in the slide boat method is smaller than that in the vertical dipping method, so there is a drawback in terms of economy.

[0017]

[Effects of the Invention] By using the epitaxial wafer of the present invention, it is possible to easily obtain a light emitting diode that generates light with a short wavelength of 940 nm or less with high efficiency.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view of an epitaxial wafer of the present invention.

FIG. 2 is a schematic cross-sectional view of a conventional epitaxial wafer.

[Explanation of symbols]

1: n-type AlxGa1-xAs layer 2: p-type AlyGa1-yAs layer 3: p-type AlzGa1-zAs layer 4: p-type AlGaAs epitaxial layer 5: p-type GaA
s epitaxial layer 6: n-type GaAs epitaxial layer 7: n-type GaAs substrate

Claims (1)

[Claims] Claim 1: Si-doped n-type AlxGa1-xAs
and p-type AlyGa1-yAs added with Si and p-type AlzG with a thickness of 5 μm to 30 μm added with Si.
An epitaxial wafer characterized in that a1-zAs are stacked in this order.