JPH041496B2 - - Google Patents

Description

[Detailed description of the invention] The present invention provides In _1-x GaxAs, In 1-x GaxAs, In _1-x
This invention relates to a liquid phase epitaxial (LPE) growth method for growing multiple epitaxial crystal layers such as GaxAsyP _1-y and InP.

Multilayer liquid-phase epitaxial growth of compound semiconductors is used in light-emitting and light-receiving devices for optical communications, such as semiconductor lasers (hereinafter referred to as LDs), light-emitting diodes (hereinafter referred to as LEDs), and avalanche photodiodes (hereinafter referred to as LEDs).
This is an important crystal growth method for obtaining elements such as APD (hereinafter referred to as APD) and photodiodes (hereinafter referred to as PD), and it is desired to establish a growth method that can obtain a high-quality grown crystal layer with few defects. Currently, light emitting devices for optical communications have oscillation wavelengths in the 0.8 to 1.6 μm range.
GaAs-GaAlAs system or InP-InGaAsP system
Research and development of LD and LED is the mainstream. Also,
Main oscillation wavelengths of GaAs-GaAlAs LDs and LEDs
PD or APD using Si single crystal is widely used as a photodetector for 0.8 μm to 0.87 μm. However, it is practically difficult to detect light with a wavelength of 1 μm or more in Si single crystal due to its small absorption coefficient, and it cannot be used in the 1.1 μm to 1.6 μm wavelength range where optical fiber has low transmission loss. Also, for wavelength range of 1.1μm or more and 1.5μm.
Although there is a Ge-APD, it is not necessarily the best photodetector for optical communications due to dark current and excessive noise. For this reason, PDs or APDs using - group compound semiconductors are required, and InGaAs, InGaAsP,
There are reports of prototype production using GaAlSb, GaAlAsSb, GaSb, etc. FIG. 1 is a reported example of a planar type APD in which a p-n junction is formed in InP using an In _1-x GaxAsyP _1-y layer as a light absorbing layer, and is described in detail in Japanese Patent Application No. 39169/1983. The shape of a wafer with this structure is to form an n ⁺ -InP buffer layer 12 on an n ⁺ -InP substrate 11, then form an n-type In _1-x GaxAsyP _1-y layer (light absorption layer) 13, and then This is a wafer on which an n-type InP layer 14 is formed, and by basically forming a p ⁺ region 15 in the InP layer 14 by selective diffusion, low dark current and high multiplication characteristics are achieved.
APD is obtained. A device structure similar to this
In _1-x GaxAs, which corresponds to the longest wavelength composition of In 1- _x GaxAsyP _1-y, which is lattice matched to InP, is used as a light absorption layer.
LD with In _1-x GaxAsyP _1-y as active layer or
Detects all wavelengths of light from light sources such as LEDs
When manufacturing APD, PD, etc., In _1-x GaxAs
It is necessary to epitaxially grow an InP layer on top. However, in the liquid phase growth method,
When trying to grow InP on In _1-x GaxAs, InP
Conversely, a so-called meltback phenomenon occurs in which the In _1-x GaxAs layer dissolves in the growth solution, making it impossible to form a multilayer structure. For this reason, a layered structure is obtained by epitaxially growing a so-called anti-meltback In _1-x GaxAsyP _1-y layer on In _1-x GaxAs and then growing an InP layer. Even in this case
In _1-x GaxAs and In _1-x GaxAsyP _1-y Anti-melt back to make the interface a good mirror surface In _1-x
The composition of GaxAsyP _1-y is required to be about x0.24 and y≧0.55, and this is discussed in Japanese Patent Application No. 56-109690.
It is described in detail. In addition, APD wafers with the same structure as above in which In _1-x GaxAs is grown as a light absorption layer with a thickness of 1.0 μm or more, or as a light source.
For LED use, a thick In _1-x GaxAsyP _1-y layer of about 2 μm is used as an active layer, and InP is placed on the In _1-x GaxAsyP _1-y layer.
When a layer is grown by liquid phase epitaxial growth, a crystal layer of relatively good quality is obtained in the central region of the fabricated wafer, but misfit dislocations are introduced in the peripheral region of the wafer, and in extreme cases, a heterogeneous layer structure is obtained. Sometimes it doesn't work. FIGS. 2 and 3 are schematic diagrams for explaining this, based on an example of fabricating an APD wafer using In _1-x GaxAs as a light absorbing layer. Figure 2 shows an n ⁺ type on an n ⁺ type InP (100) substrate 21.
- After growing InP22 by LPE, grow n-type In _1-x GaxAs23 to 2 μm to satisfy lattice matching conditions at the growth temperature.
degree, then anti-meltback n-type In _0.76 Ga _0.24
This is a cross section of an As _0.55 P _0.45 layer 24 grown by LPE to a thickness of about 0.5 μm. At this time, at the peripheral edge 28 of the wafer,
An abnormal growth called so-called edge growth has occurred in the In _1-x GaxAs layer 23, and the In _1-x GaxAs
This is particularly noticeable when the layer thickness is 1.0 μm or more, and can reach a height of several tens of μm. Next, FIG. 3 shows an example of the results when InP is continuously grown by LPE on such a wafer. In the central region 20 of the wafer, even after growing the n-InP layer 25, relatively good crystallization is observed. Compared to having a gender,
In the peripheral region 28 of the wafer, In _1-x GaxAs 23 and In _1-x GaxAsyP _1-y that have grown over time
The layer 24 dissolves into the InP growth solution and disappears, and a large number of misfit dislocations 29 are generated in the InP layer 25 starting from that region. Furthermore, such misfit dislocations occur in the central region 20 of the wafer.
It is often the case that the plant grows to a certain extent, and a growth method that achieves good quality is desired.

As mentioned above, the object of the present invention is particularly to In _1-x
GaxAs or In _1-x GaxAsyP A method that creates a high-quality epitaxial growth layer with few defects and excellent uniformity by devising a multilayer liquid phase epitaxial growth method that requires a relatively thick film of _1-y layers. It is.

The liquid phase epitaxial growth method of the present invention includes at least In _1-x GaxAs or In _1-x GaxAs on an InP substrate.
GaxAsyP _1-y (0.47>x≧0.24, 1>y≧0.55) Step of forming a liquid phase epitaxial growth layer and contacting the substrate wafer on which the liquid phase epitaxial growth layer is formed with an InP epitaxial growth solution. After moving the InP epitaxial growth solution without contacting the peripheral edge of the substrate wafer before InP epitaxial growth, the InP layer is liquid-phase epitaxially grown.

Next, the advantages of the present invention will be explained based on one embodiment. This example shows an example of crystal growth of an APD and PD wafer using In _1-x GaxAs as a light absorption layer, and Fig. 4 shows an example of a liquid phase epitaxial growth apparatus for realizing the method of the present invention. . Growth boat 1 was prepared so that at least In _1-x GaxAsyP _1-y quaternary composition x and y could be lattice matched with InP.
In _1-x, a mixture of In, GaAs, InP, and InAs
GaxAsyP _1-y growth solution 2 and the In _1-x
It has a solution storage boat part 3 having a smaller bottom surface than the bottom surface of the GaxAsyP _1-y growth solution storage boat, and by moving the InP substrate crystal 4 in the direction shown by the arrow 5 in the figure, the above In _1-x It can be contacted with the GaxAsyP _1-y growth solution 2 and an In _1-x GaxAsyP _1-y layer can be grown by LPE. Further, the growth boat has a boat 6 separate from the growth boat 1 on the growth solution storage boat 3, and the boat 6 is equipped with an InP growth solution 7 containing a mixture of In and InP. , the InP substrate 4 is in contact with the growth solution 2 for a predetermined time In _1-x
After the GaxAsyP _1-y layer is grown by LPE, the InP substrate 4 can be moved under the growth solution storage boat section 3 by moving the InP substrate 4 in the direction of the arrow 5 in the figure. At this time, after confirming in advance that the periphery of the In _1-x GaxAsyP _1-y growth layer on the InP substrate 4 does not appear on the bottom surface of the growth solution storage boat by the distance the InP substrate 4 is moved (arrow direction 5 in the figure), By moving the boat 6 in the direction of arrow 8 in the figure, the InP growth solution 7 is poured into the growth solution storage boat section 3. After this operation, by holding for a predetermined time, an InP layer of a predetermined thickness can be obtained, and the liquid phase growth method of the present invention can be realized. FIG. 5 shows a schematic cross section of an example of crystal growth of an APD and PD wafer using In _1-x GaxAs as a light absorption layer. The growth boat is a horizontal slide boat that has at least the components shown in Figure 4 above, and the growth method is, for example, held at a saturation temperature of 650°C for about an hour, then rapidly cooled, and once the temperature reaches 640°C.
By moving the n ⁺ -InP substrate 31 under the InP buffer layer growth solution, the n ⁺ InP buffer layer 32 is grown.
Grow the In solution at 650℃ once it reaches 637℃.
Under a solution containing a certain amount of Ga and As,
By transferring the InP substrate 31, the growth of the n ⁺ InP buffer layer 32 is stopped, and the n-type In _1-x continues to grow.
GaxAs layer 33 is grown. Next, when the temperature reaches 635℃, the temperature decrease is shifted to 0.2℃/min, and the
After growing In _1-x GaxAs33, it was added to In solution at 650℃.
Wavelength composition containing predetermined amounts of Ga, As, and P
1.3 μm equivalent of In _1-x GaxAsyP _1-y grown under the above-mentioned
In _1-x GaxAs by transferring the InP substrate 31
An n-type In _1-x GaxAsyP _1-y layer 34 is grown on the layer 33 by LPE. By growing here for about 10 seconds
An In _1-x GaxAsyP _1-y layer 34 of about 0.5 μm is obtained. This growth corresponds _to the LPE growth using the growth solution ₂ explained in FIG. By growing layer 35 for a predetermined period of time, the LPE crystal wafer of FIG. 5 is produced. In this example, the InP growth solution comes into contact with the abnormal growth region at the LPE growth edge of the In 1 _{-x GaxAs} layer and the anti-meltback In _1-x GaxAsyP _1-y layer region on the In 1-x GaxAs. By growing the InP layer by LPE only in the region excluding the abnormal LPE growth region, the heterolayer structure under the InP growth layer can be improved compared to the case explained using FIGS. 2 and 3 above. The introduction of misfit dislocations, which are slip dislocations, into the slant and InP layers is completely suppressed, and a high-quality crystal for APD can be obtained.

In the example, InP−InGaAs−InGaAsP−InP
Although we have described an example of creating a layered structure, InP−
The same holds true when producing InGaAs-InP and InP-InGaAsP-InP layer structures.

Above, we have described crystal growth for APD or PD using In _1-x GaxAs as the light absorption layer, but APD or In _{1 -x} GaxAsyP _1-y that requires a relatively thick film as _the light absorption Even in LEDs etc. in which _{the -x} GaxAsyP _1-y layer is the active layer, in the device structure where the InP layer is liquid-phase epitaxially grown on the In _1-x GaxAsyP _1-y layer, 0.47>x≧0.24, 1> It is known that abnormal growth at the wafer edge is large in In _1-x Gax AsyP _1-y liquid phase epitaxial growth with a composition of y≧0.55, and thick film In _1-x GaxAs or In _1-x
It is useful for liquid phase epitaxial growth of multilayer structures requiring GaxAsyP _1-y layers, and provides high quality epitaxial growth layers.

[Brief explanation of drawings]

Figure 1 shows a reported example of APD using In _1-x GaxAsyP _1-y , 11 is n ⁺ -InP substrate, 12 is n ⁺ -
InP buffer layer, 13 is n-type In _1-x GaxAsyP _1-y
Layer 14 is an n-type InP layer, and layer 15 is a layer in which p-type impurities are formed by selective diffusion technology. Figure 2 shows the abnormal growth at the growth edge when an In _1-x GaxAs layer is grown by liquid phase epitaxial growth, 21 is an n ⁺ -InP substrate, 22 is an n ⁺
-InP buffer layer, 23 is n-type In _1-x GaxAs layer,
24 is an n-type In _1-x GaxAsyP _1-y layer. FIG. 3 shows a cross section of a wafer when an n-type InP layer 25 is grown in a liquid phase on the wafer shown in _FIG . _1-x GaxAsyP _1-y InP via layer 24
When layer 25 is grown, In _1-x GaxAs and In _1-x
This shows that the GaxAsyP _1-y layer has melted and misfit slip dislocations have extended into the n-InP layer 25 starting from this region. FIG. 4 shows a liquid phase growth apparatus for implementing the method of the present invention, in which 1 is a boat used for carrying out liquid phase growth;
2 is a growth solution; 3 is a boat containing a growth solution in which epitaxial growth is to be continued after the growth in 2; 4 is a substrate crystal; and 5 is an arrow indicating the moving direction of the substrate crystal. 6 is a boat having a different configuration from the boat 1, 7 is a growth solution, and 8 is an arrow indicating the direction in which the boat 6 is moved, representing the operation of pouring the growth solution 7 into the growth solution storage boat section 3. .
FIG. 5 shows a cross section of a multilayer structure wafer obtained by the liquid phase epitaxial growth method of the present invention, where 31 is an n ⁺ type InP substrate and 32 is an n ⁺ − type InP substrate.
InP layer, 33 is n-type In _1-x GaxAs layer, 34 is n-type
In _1-x GaxAsyP _1-y layer, 35 is an n-type InP layer.

Claims (1)

[Claims] 1 At least In _1-x GaxAs or
In _1-x GaxAsyP _1-y (0.47>x0.24, 1>y≧
0.55) After forming a liquid phase epitaxial growth layer and moving the substrate wafer on which the epitaxial growth layer has been formed without contacting the InP epitaxial growth solution, the InP epitaxial growth solution InP is deposited on the liquid phase epitaxial growth layer without contacting the peripheral edge of the liquid phase epitaxial growth layer of the substrate wafer before growth.
A liquid phase epitaxial growth method comprising the step of liquid phase epitaxial growth of a layer.