JPS63207120A - Vapor growth method - Google Patents

Abstract

PURPOSE:To obtain preferable crystallinity in an epitaxial layer grown on a GaAs substrate of plane (100) by heat treating the substrate in arsine (AsH3) at higher temperature than a growth temperature before the layer is epitaxially grown on the substrate. CONSTITUTION:In a vapor growth method of by a chloride transporting process at 750 deg.C or lower on a GaAs substrate of plane (100) + or -0.5 deg., the substrate is heat treated, before the vapor growth, at 850 deg.C or higher in arsine (AsH3), and grown at the growth temperature. That is, in order to obtain a preferable crystal on the GaAs substrate of (100) + or -0.5 deg., it must be heat treated at least at 780 deg.C, but according to this method, an epitaxial layer having an excellent quality can be grown on a region having preferable film thickness and impurity control at 750 deg.C or lower.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Field of Application) The present invention relates to a method for growing an epitaxial layer with excellent substrate quality on a GaAs substrate of (100) plane ±0.5°.

(Prior art) In the chloride transport method vapor phase growth, the conventional substrate (1
It was common to use a surface polished at an angle of 2° to 5° from the 00) surface. The reason is (100) plane ±0
．． When grown on a substrate surface with an angle of 5°, many gentle hill-like protrusions appear, making it difficult to achieve high uniformity in the thickness of epitaxial droplets during the process of device fabrication, such as exposure of photoresist using a mask, or within a wafer. This becomes a major hindrance in the required processing steps for manufacturing devices, and ultimately causes a deterioration in the effective area utilization rate per wafer. As mentioned above to solve this problem (
A crystal substrate surface tilted by 2° to 5° in the <110> direction or (011> direction) from the (Zoo) plane is used.

Therefore, under optimal conditions, it is possible to achieve high uniformity in which both carrier concentration and film thickness can be suppressed to within 2 inches on a 2-inch diameter substrate surface, making it practical for planar field effect transistors, semiconductor lasers, photodetectors, etc. has been done. However, in complex device structures such as semiconductor lasers, there is a process in which the width of the active layer is controlled by mesa type I etching to narrow the current in the active layer, or in which multiple elements are integrated on one substrate. For those that include processing steps for etching, %(Zoo) planes tend to appear in the wet etching and reactive gas phase etching steps, which causes a problem that the substrate surface becomes asymmetric in the off direction.

(Problems to be Solved by the Invention) As described above, the conventional vapor phase growth method has the problem that the (100) plane tends to appear in the etching process, resulting in asymmetrical properties in the off-direction of the substrate surface.

The present invention improves the drawbacks of the conventional method described above, and
An object of the present invention is to provide a method for depositing an epitaxial layer with excellent crystallinity on an (ioo) plane GaAs substrate.

[Structure of the invention]

(Means for solving the problem) In the present invention, before performing epitaxial growth on a (100) plane Ga As substrate, the substrate is grown at a temperature higher than the growth temperature.
This is a vapor phase growth method in which heat treatment is performed in s H1 to maintain good crystallinity of the epitaxial layer grown thereon.

(Function) (Zoo) ±0.5° The surface Ic of the GaAs substrate C. There are terrace-like irregularities of several microns in size, less than a few i layers, and when grown on this (100) plane, especially In the case of chloride-transporting vapor phase growth, which is very sensitive to the substrate surface, growth starts from scattered steps, resulting in an appearance similar to superimposed island-like growth, and dislocations occur from the boundaries between islands. It was discovered that this occurs and it is difficult to grow a good epitaxial layer. Furthermore, in order to perform mirror growth, it is necessary to supply fine steps on the atomic order so that horizontal growth (adsorption and movement, bonding as crystals) and vertical growth are balanced, and this step density is a GaAs substrate A s H, (850
It has been found that this can be obtained by heat treatment at a temperature of 0.3 °C or higher. (ioo)±0.5°In order to obtain a good crystal on a GaAs substrate, the temperature must be at least 780°C or higher, but if the present invention is used, the quality can be maintained at 750°C or lower with good film thickness and impurity control. can grow an excellent epitaxial layer.

(Example) Hereinafter, details of the present invention will be explained with reference to illustrated embodiments.

As an example, GaAs(ioo)±
The case of growth on a 0.5° substrate will be described using FIG. The well-known hydride vapor phase growth equipment (
Insert the GaAs substrate (Zoo) ±0.5°, 1
Flow 100 CC/min of AsH diluted with hydrogen, 8
Heat treatment is performed at 50° C. for 20 minutes, and a step for growth is uniformly applied to the substrate as in step 3. Kiriagas uses H2 to make the total flow rate 1.517 minutes. After that, growth @
GaAs 4 is grown at 700°C. The growth conditions for GaAs are H (490
CC/min, ASH, 90 CC/min, and the temperature of Ga metal is 850°C. When manufacturing a GaAs/InGaAsP-based semiconductor laser wafer, a Huff layer n-GaAs, an n-InGaP clad layer, a GaIn
AsP active layer, p-InGaP crat layer, p-GaA
It is only necessary to grow the s-contact layer after heat treatment of the substrate, and by performing heat treatment of the substrate, a free device structure can be formed.

Figure 2 shows an investigation of the crystal quality of the epitaxial layer when the heat treatment temperature of the substrate was changed. Heat treatment of the substrate A
Conducted for 30 minutes while sH was flowing at 100 CC/min,
Thereafter, GaAs was grown at 700° C., and its crystallinity was etched with KOHOH molten nicht, and the number of etch pits was counted. Since the etch pit (dislocation density) of the substrate itself is in the range of lXl0'52X10''♂,
In heat treatment at 850°C or higher, the dislocation density is suppressed to the same level as that of the substrate itself.

On the other hand, the dislocation density of the epitaxially grown layer increases rapidly when heat treated at a temperature lower than 850°C.

Further, FIG. 4 shows the results of examining the dislocation density when epitaxial growth was performed at 700° C. by changing the heat treatment time at 850° C. Good crystals can be obtained by heat treatment for 10 minutes or more.

If crystal growth is to occur at a temperature below 750°C,
If the substrate is not heat-treated and the epitaxial layer 2 grows with a large step size and sparse steps as shown in FIG. 3, dislocations will occur from the boundaries of the crystals grown on each step. The surface also becomes morphological with emphasized unevenness.

Note that the present invention is not limited to the embodiments described above. In the above embodiment, the epitaxial growth of GaAs/InGaAsP was applied, but as long as a GaAs substrate is used, for example, GaA with a gradually changing composition can be grown on GaAs.
It is also effective when depositing xP. Further, it can also be applied to chloride vapor phase epitaxy, which is a chloride transport method different from hydride vapor phase epitaxy. others,
Various modifications can be made without departing from the spirit of the invention.

〔Effect of the invention〕

According to the present invention E, the substrate is heat-treated at 850° C. or higher,
By providing a step for flat growth on the substrate surface as shown in FIG. 1, epitaxial growth with any combination can be realized and good crystal quality can be obtained.

[Brief explanation of the drawing]

1 to 4 are diagrams for explaining the present invention.

Claims (1)

[Claims] 750°C on a GaAs substrate with (100) plane ±0.5°
In the method of vapor phase growth using the chloride transport method described below, the substrate is heat treated in arsine (AsH_3) at a temperature of 850°C or higher before the vapor phase growth, and then the growth is performed at the growth temperature. vapor phase growth method.