JPH02101737A - Compound semiconductor wafer - Google Patents

Abstract

PURPOSE:To make a compound semiconductor epitaxial wafer which is excellent in mass productivity, small in bending and large in area without cracking by adding germanium to Ga1-xAlxAs which is epitaxially grown in solid phase on an GaAs substrate. CONSTITUTION:On a GaAs substrate with the aid of solution consisting of Ga, GaAs, Al and Ge, by liquid-phase epitaxial growth method, Ga1-xAlxAs(0.4< x<1) epitaxial layer of not less than 3X10<17>cm<-3> for Ge concentration is formed at a growth starting temperature of 900 deg.C. At this time, the curvature of a wafer is 200mum or less, and there is no generation of cracks in the surface of the epitaxial layer nor in the GaAs substrate, etc. Next, the surface of the epitaxial layer is polished so as to make the thickness of the epitaxial layer into 250mum, and next GaAs substrate side is polished and the GaAs substrate is removed completely, thus Ga1-xAlxAs wafer of 200mum in thickness, consisting of Ga1-xAlxAs alone, is obtained. Hereby, a compound semiconductor wafer can be obtained which is small in bending even if the AlAs mixed crystal ratio x of Ga1-xAlxAs is 0.4 or more and the thickness is 100mum.

Description

Detailed Description of the Invention [Industrial Field of Application J] The present invention is directed to GaAlA having a high AfJAS mixed crystal ratio and a thick film thickness.
The present invention relates to a compound semiconductor wafer in which an s epitaxial layer is grown on a GaAs substrate, or a compound semiconductor wafer made of GaAjAs from which the GaAs substrate of the wafer is completely removed.

[Prior Art] Conventionally, wafers in which Ga1-xAlxAS is epitaxially grown on a GaAs substrate have been widely used for field effect transistors (FEETs), light emitting diodes (EDs), and the like.

In LED, G"1-XΔf on GaAsl5 plate
1xAsll functions as a light transmission layer for the purpose of improving the light emission output, but the nJ viewing L with a light emission wavelength of 7000A or less
In ED, Ga1-xAll and XAs8 are required to have an AjAs mixed crystal ratio X of 0.4 or more and a thickness of 100 μm or more. Preferably, the GaAs substrate that absorbs light is removed and Ga1-xAρxAs[ is used as the substrate.

The conductivity type of this Ga1-xAfJxAS layer is selected depending on the structure of the LED, but in the case of a structure in which current is passed through the Ga1-xAfJxAs layer, an n-type or p-type layer is doped with Zn or -1-e. In the case of a structure in which no current is applied, a non-doped layer with a low carrier concentration is generally used.

[Problem to be solved by the invention] By the way, the lattice constant of GaAs and AJIAs is about 900.
℃, but the thermal expansion coefficient α is -〇-1 α = 6.8X10 ℃, α = 5.2Ga
AsAfJAs×10℃
different from. The thermal expansion coefficient of Ga1-xAfJxAS is α
and α GaAs All As, and △fJ
It is determined by the As mixed crystal ratio X. Therefore, AfJAS
The higher the mixed crystal ratio X, the closer the thermal expansion coefficient is to α/JAs,
It also approaches low culm αGaAs. In fact, when Ga1-xANxAs is liquid-phase epitaxially grown on a QaASW plate at about 900°C, the lattice constants of the two are almost the same regardless of the size of the AρAS mixed crystal ratio X at the growth temperature, but when cooled to room temperature. When taken out, as shown in FIG. 2, the GaAs substrate 2 and Ga 1-x A fJ
Due to the difference in thermal expansion coefficient with s BJ 3, T
a 1-x A'J x A SHA It curves convexly toward the 3 side. Our experiments have confirmed that there is almost no difference in the curvature of this wafer among non-doped, Zn-doped, and Te-doped wafers. In addition, the size of the curvature is determined by the large area of the wafer and Ga1-xAfJxA.
The higher the AIIAS mixed crystal ratio X of the S layer 3, the more remarkable it is.
If the thickness of one layer is 1100u or more, the curvature is 30
There is a problem in that when the thickness reaches 0 μm or more, cracks occur in the wafer, making it extremely difficult to form the element f.

Therefore, until now AjAs mixed crystal ratio mixed crystal high XGa1-
It is not possible to mass produce large area wafers on which xAgxAS layers are epitaxially grown, and a solution to this problem has been strongly desired. Also, even if you try to remove the GaAs substrate and manufacture a Ga1As substrate, it will not be possible to produce a flat G1 because the glass is greatly curved.
It is not possible to obtain a1-xAfJxAS substrate, and GaA
There is a problem in that when the s-substrate is removed by polishing, the wafer breaks.

In view of the problems of the prior art described above, an object of the present invention is to
IIAS mixed crystal ratio X is 0.4 or more and thickness is 100 μm
The above Ga1. , x All

[Means for Solving the Problems] The gist of the present invention is to provide Ga1-x A'J x AS (0,4≦
x (1, thickness 100 μm or more) with germanium 3 x
The reason is that more than 1017 ctx-" is added.

[Example 1 Fig. 1 shows Ga1. The relationship between the dopant and carrier concentration of the Aρx AS epitaxial layer and the magnitude of wafer curvature is shown. The wafer has a diameter of 40 m and a GaAs substrate thickness of 3
The thickness of the 50 μm 1G a 1-x A j xAS epitaxial layer is 300 μm, and the Al1As mixed crystal ratio is 0.4. The dopant in the epitaxial layer is Te.
In the case of 1Zn, the curvature of the wafer is 3 regardless of the gearia concentration.
00 μm or more, in many cases (60-80%)
Cracks are generated on the surface of the G a 1-x A j x As epitaxial layer.

- In the case of Ge doping, the magnitude of the curvature decreases as the carrier concentration increases, and the carrier concentration force is 3 × 101
7c! ll-3 or more Tehau J Hano Curved Ha2o.

It is less than μm, and no cracks are observed on the surface of the epitaxial layer. For the above reasons, carrier 1 in the case of Ge doping
1 degree is preferably 3 x 1017ax-3 or more.

In addition, Ga1-x AJ x As AρA of the Evita gal layer
By applying the present invention even when the S mixed crystal ratio

The characteristics, thickness, etc. of the GaAs substrate can be arbitrarily selected, and in any case, a sufficient effect of 1q can be obtained.

Furthermore, in the present invention, the concentration of Ge in the Ga1-xAll There is no problem even if the substances are added at the same time, but rather, the practicality of the wafer is improved by arbitrarily selecting them to control electrical characteristics and the like.

As described above, according to the present invention, it is possible to obtain a wafer with small curvature, so even if the wafer has a large area, mass production is possible without cracking the wafer surface. or,
When the GaAs substrate is removed by polishing, the obtained Ga1
-x 11x As the strain applied to Asll is small, Ga1-x AN xAs is almost flat without cracking.
Wafers can be obtained with high yield.

Example 1 Diameter 40 aw, thickness 350 μm 1 Crystal plane orientation (100)
A 400 um thick Ge(r)-concentrated a
3 X 1017am-3(f)Ga1-xA! Jx
An As (X=0.4-0.5) epitaxial layer was formed. The wafer curvature at this time was 200 μm or less, and no cracks were generated on the surface of the epitaxial layer, the GaAs substrate, etc.

Next, the surface of the epitaxial layer was polished to a thickness of 250 μm, and then the QaAS substrate side was layered, and the entire GaAs substrate was removed, and the Ga1. All x
Qa A with a thickness of 200 μm consisting only of Aslil
fJ, As wafer was obtained. No cracks were generated during the polishing process, and the above wafer could be manufactured with a yield of 90% or more.

Example 2 Diameter 40 mm, thickness 350 μm 1 crystal plane orientation (100>G a AS ki root plate Ga, GaAs.

The film was grown to a thickness of 40°C by liquid phase epitaxial growth using a solution consisting of AI, Ge, and In at a growth starting temperature of 900°C.
P-type Ga with 0 μm and carrier concentration of 1×10181
Aj As (X=0.4 to 1−××0.5) epitaxial layer was formed. Here, Ge was added so that the i degree in the Ga, -xAJI xAs epitaxial layer was 3X1011α-3. At this time, the curvature of the wafer was 200 μm or less as in Example 1, and no cracks were generated. Further, polishing was performed in the same manner as in Example 1, and a high yield of P-type Ga1-xA11xAs epitaxial wafers was obtained.

[Effects of the Invention] As explained above, according to the present invention, Oa1. AN XAs
By adding 3x10 ax or more of Ge to the layer, the ΔjAs mixed crystal ratio X of Ga1-xAlxAS is 0.4.
As described above, a compound semiconductor chip with small curvature can be obtained even if the thickness is 100 μm or more. Therefore, a large area of compound semiconductors can be produced at a high yield without cracking the wafer surface. . Also, G
When removing the aAs substrate, the GaA11) As wafer obtained is 1-x due to the small distortion due to curvature.
x It is possible to obtain flat Ga1-xA1x AS wafers with high yield without cracking.

[Brief explanation of the drawing]

Figure 1 shows Ga, -xA, I! An explanatory diagram showing the relationship between the carrier concentration of the xAs epitaxial layer and the degree of curvature of the wafer.
XAs1i! FIG. 2 is an explanatory diagram showing a compound semiconductor wafer at room temperature that has been subjected to liquid phase epitaxial growth. 1: Wafer, 2: GaAs substrate, 3: Ga1-x1)xAs.

Claims (1)

[Claims] 1. AlAs mixed crystal ratio X is 0.4≦X<1 and the thickness is 100% by liquid phase epitaxial growth on a GaAs substrate.
In a wafer on which a Ga_1_-_xAl_x AS layer of μm or more is formed, the Ga_1_-_xAl_x
Germanium in the AS layer is 3 x 10^1^7cm^-^3
A compound semiconductor wafer characterized by containing the above additives. 2. The compound semiconductor wafer according to claim 1, wherein the GaAs substrate is completely removed.