JPH0450197A - Method for vapor growth of compound semiconductor - Google Patents

Abstract

PURPOSE:To form an epitaxial layer, capable of emitting light at a short wavelength and having hardly any defects by controlling the growth temperature and flow rate of a raw material gas under specific conditions in epitaxially growing a GaInP mixed crystal on a GaAsP mixed crystal substrate according to a metal organic chemical vapor growth method. CONSTITUTION:A GaxIn1-xP mixed crystal (x is 0.65-0.75) to be lattice coherent with a GaAsP mixed crystal substrate is epitaxially grown thereon under reduced pressure according to a metal organic chemical vapor growth method. In the process, the following means are adopted. That is the growth temperature (Tg) is set within the range of 720 deg.C<=Tg<=755 deg.C. The raw material gas flow rates are controlled so as to afford 1.1r+402<=Tg<=1.1r+432 when the molar ratio of PH3 gas which is a raw material for a group V element to the organometallic gas which is a raw material for a group III element is (r).

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for vapor phase epitaxial growth of compound semiconductors, and is particularly suitable for use in growing compound semiconductor mixed crystals by low-pressure MOCVD (metal-organic chemical vapor deposition) method. related to technology.

[Prior Art] In recent years, compound semiconductor crystals such as GaAs and InP have been used as materials for ultrahigh-speed digital devices and optical devices. Among these, optical devices in which a mixed crystal such as QaInP, which is lattice-matched to the GaAs substrate, is epitaxially grown on the GaAs substrate have been put into practical use.

By the way, epitaxial growth techniques for compound semiconductors include VPE (vapor phase epitaxial growth) and MOC.
The VD method and the MBE method (molecular beam epitaxial method) are known. Among these, the MOCVD method is used for the epitaxial growth of the ■-■ group compound semiconductor mixed crystal because it has good film thickness controllability and is suitable for mass production.

[Problems to be Solved by the Invention] Optical devices that have been put into practical use in the past have been made by epitaxially growing QaInP mixed crystals on GaAs substrates by MOCVD, and their emission wavelength is 660 nm.
nm, and no emission of shorter wavelengths could be obtained. In addition, attempts have been made to grow a GaInP mixed crystal on a GaAsP mixed crystal substrate to lattice match it in order to obtain light emission with a shorter wavelength.
Using the conditions for epitaxial growth of Ga I nP mixed crystal on an As substrate, or conditions in the vicinity thereof, Ga
The InP mixed crystal surface has a drawback in that a large number of elliptical protruding defects occur. Optical devices having such mixed crystals with many defects have poor luminous efficiency, which causes a decrease in yield.

The present invention has been made to solve the above-mentioned drawbacks, and its purpose is to provide an epitaxial growth technique capable of emitting short wavelength light and forming a mixed crystal epitaxial layer with few defects.

[Means for Solving the Problems] The inventors have developed a method using low-pressure MOCVD on a GaAsP mixed crystal substrate.
Various experiments were conducted in order to find out the growth conditions that minimize the protrusion-like defects when epitaxially growing a QaInP mixed crystal layer using the method.

As a result, it was found that the surface state of the mixed crystal layer mainly depends on its growth temperature and the molar ratio of the group (1) source gas and the group (2) source gas.

FIG. 1 shows the surface state of the grown mixed crystal film when the growth temperature and the molar ratio of the group Ⅰ element raw material and the m group element raw material were varied. The data in the figure uses triethylgallium, trimethylindium, and 50% H8 diluted phosphine (PH,) as raw materials, and the carrier gas (H8) flow rate of triethylgallium and trimethylindium is constant (
300 secM and 1703 CCM), and the molar ratio was changed by changing the PH and gas flow rate.

In the figure, the marks, I, and ■ mark indicate that protruding defects were generated on the surface of the mixed crystal, and Δ and mu marks indicate that surface roughness was generated due to minute defects. On the other hand, ○
The mark indicates that the surface had a good surface condition with a micro defect density of 100 pieces/cnl or less and a protrusion defect density of 300 pieces/d or less.

In addition, marks are those with a protrusion defect density of more than 300 pieces/a+I and less than 1,000 pieces/d, and 1 mark is those with a protrusion defect density of 1,000 pieces/cnf or more and less than 10,000 pieces/d. , - indicates a protrusion defect density of 10,000 pieces/d or more.

In addition, Δ marks indicate that the microdefect density exceeds 100 pieces/d, and 10
,000 defects/d, and the square mark indicates that the micro/J% defect density is 10,000 defects/d or more.

From Figure 1, when the growth temperature is 720°C or lower, many protruding defects occur, and when the growth temperature is 755°C or higher,
It can be seen that surface roughness with many micro defects occurs. In addition, the flow rate ratio of the V group raw material gas and the M group raw material gas is r, and the temperature is T.
g('C), Tg=1.1r+432 in the graph
When we draw the straight line A of , and the straight line B of Tg=1.1r+402, we get
It can be seen that surface roughness occurs on the left side of straight line A, and protruding defects occur on the right side of straight line B.

The present invention was made based on the above findings, and Ga
GaxI, which is lattice matched to the A s P mixed crystal substrate, is
When epitaxially growing an n, And when r is the molar ratio of the PH gas which is the raw material of the V group element and the organometallic gas which is the raw material of the M group element, 1
．． It is proposed to perform epitaxial growth by controlling the flow rate of the source gas so that 1r+402≦Tg≦1.1r+432.

[On the G a A s P mixed crystal substrate, G a I n,
When a P mixed crystal layer is grown by the MOCVD method, if the growth temperature is too high or the ratio of the raw material gas for phosphorus, which is a group Ⅰ element, is small, phosphorus escapes from the substrate or the mixed crystal layer, which tends to cause surface roughness. It is thought that when the ratio of phosphorus in the source gas increases, GaInP particles grow on the surface of the GaAsP mixed crystal substrate, and these particles serve as nuclei to cause abnormal growth and increase the number of protruding defects.

However, according to the above-mentioned means, the growth temperature Tg is set to 720
℃ or higher and 755℃ or lower, and 1.1r+402≦Tg
Since the flow rate of the raw material gas is controlled to satisfy the condition ≦1.1r+432, it is possible to prevent phosphorus from being removed from the substrate or the mixed crystal film and to suppress abnormal growth, which improves the surface condition. Good growth of GaInP mixed crystal becomes possible.

[Example] The growth temperature was set to 740°C, and the pressure inside the container was set to 0.1 atm.
and the concentration and flow rate of the raw material gas are determined so that the molar ratio r of the raw material of the group Ⅰ element and the raw material of the group m element is 290. 14. Ga..., In on the mixed crystal substrate. A 1P mixed crystal was epitaxially grown to a thickness of 2 μm by low pressure MOCVD.

After the growth was completed, the surface of the mixed crystal layer was observed using an optical microscope. As a result, there was no roughness on the substrate surface, and the number of elliptical protruding defects was good at less than 300/d, and the size of the protruding defects was reduced to one quarter both vertically and horizontally compared to the conventional method. .

As explained above, the present invention provides a GaAsP mixed crystal substrate with a GaxIn-xP mixed crystal (x=0
．． 65 to 0.75) by low pressure organometallic vapor phase epitaxy, the growth temperature Tg was set to 72
When set in the range of 0°C≦Tg≦755°C, and when r is the molar ratio of the PH gas, which is the raw material for the V group element, and the organometallic gas, which is the raw material for the M group element, 1,1r+402≦Tg≦
Since epitaxial growth is performed by controlling the flow rate of the raw material gas so that the ratio of This has the effect of making it possible to grow a GaInP mixed crystal with good quality.

[Brief explanation of the drawing]

Figure 1 shows GaIn on a GaAsP mixed crystal substrate under various conditions.
FIG. 3 is a diagram showing the quality of the surface state of the grown mixed crystal in the case where the P mixed crystal layer is epitaxially grown by the low-pressure MOCVD method in relation to the growth temperature and the molar ratio of the V group and M group raw material gases.

Claims (1)

[Claims] (1) G on the GaAsP mixed crystal substrate, which is lattice matched to this
a_xIn_1_-_xP mixed crystal (x=0.65~0.7
5) is epitaxially grown by metal organic vapor phase epitaxy under reduced pressure, the growth temperature Tg is set to 720°C≦T.
g≦755°C, and when r is the molar ratio of PH_■ gas, which is a raw material for Group V elements, and organometallic gas, which is a raw material for Group III elements, 1.1r+402≦Tg≦1.
1. A method for vapor phase growth of a compound semiconductor, characterized in that epitaxial growth is performed by controlling the flow rate of a source gas so that the ratio becomes 1r+432.