JPH029796A - Production of gallium arsenide single crystal - Google Patents

Abstract

PURPOSE:To reduce dislocation by the effect of hardening with impurities by simultaneously adding Al and In when a GaAs single crystal is produced by a horizontal boat method or the vertical Bridgman method. CONSTITUTION:When a GaAs single crystal is produced by a horizontal boat method or the vertical Bridgman method, Al and In as neutral impurities are added each at 1X10<17>-1X10<18>/cm<3> concn. and a single crystal is grown. The electrical conductivity of the GaAs single crystal may be any of n-type and p-type. In the case where epitaxial growth is carried out on the resulting substrate, lattice unconformability is not caused at all.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for producing a gallium arsenide single crystal, particularly a gallium arsenide single crystal having few crystal defects and having aluminum and indium added simultaneously.

[Prior Art] Gallium arsenide (GaAs) single crystals have recently been used increasingly as substrates for light emitting devices and integrated circuits, such as semiconductor lasers. However, with this GaAs single crystal, it is difficult to obtain a large dislocation-free crystal like silicon (Sl), which has been used conventionally.
In As single crystals, dislocations degrade the lifetime of lasers, and in integrated circuits, dislocations can degrade the uniformity of threshold voltages of many field effect transistors fabricated within a single substrate. I've come to understand.

As mentioned above, dislocations in semiconductor single crystals have an adverse effect on various semiconductor devices, and therefore, GaAs single crystals are also required to have fewer dislocations. Methods to reduce dislocations in single crystals include (1) reducing thermal stress during single crystal growth, (2) adding impurities,
It can be roughly divided into two types: Hardening of impurities increases critical stress.

Regarding the method (1) above, for example, liquid sealed pulling (
In the LECJ method, the hot zone is improved and a magnetic field is applied to the raw material melt during single crystal growth to reduce the temperature gradient and lower dislocations.

Regarding the method (2) above, various impurities have been investigated as additives, but as a result, indilum (In)
is generally widely used because it has a large impurity curing effect and has little effect on electrical properties.

By employing these methods, conductive GaAs crystals can be made with no dislocations or close to it on a substrate with a diameter of 50111, and semi-insulating GaAs crystals can be made with dislocation densities of 1000 to 2000c+g-'' or less. It is commercially available.

[Problems to be Solved by the Invention] The reduction of dislocations by reducing the temperature gradient in (1) above can be achieved by improving the hot zone, installing a magnetic field application device, etc.
The A-building equipment would have to be modified, which would pose technical and economical problems. In method (2), for example, when adding In, the In concentration in the crystal needs to be as high as 10'°C11-' or more, and the effective diffraction coefficient of In is extremely small (2x70-' 2) Therefore, the concentration difference in the longitudinal direction of the crystal is large, and the density of the substrate collected from one single crystal is significantly reduced.

Furthermore, when GaAs is epitaxially grown on a substrate, there is a problem that lattice mismatch occurs.

An object of the present invention is to provide a method for manufacturing a GaAs flower crystal with a low dislocation density, which reduces dislocations by the effect of impurity hardening and does not cause lattice mismatch during epitaxial growth.

[Means for Solving the Problems] The method of the present invention involves the production of gallium arsenide (GaAs)In crystals by the horizontal boat method or the vertical Bridgman method by adding additives (7) and aluminum (7), which is a neutral impurity.
AJ) ) and indium (In) at 1×10
17-1: <1×10 17 ci-', which is added at 4 degrees.

[Effect] By adding A1 and In at the above concentration, GaA
The dislocation density of the s single crystal is significantly reduced.

The so-called shirtful set dislocations include screw dislocations and 60° dislocations. Further, the 60° dislocation has an edge-like component, and there are α dislocation in which the edge of the extra half-atomic plane accompanying this is an As atom, and β dislocation in which the edge is a Ga atom. Although the addition of In increases the critical stress when α-dislocations occur and suppresses the generation of α-dislocations, the effect on β-dislocations is small.

However, the occurrence of β-dislocation can be effectively suppressed by adding Ajl.

From this, by adding In and A1 at the same time,
The generation of dislocations can be suppressed at a lower concentration than when only In or AJ is added.

If the concentration of AI is too high, it will become GaAJIAs, and if the concentration of In is not high, it will become InGaAs, which will affect the forbidden band width in quantum theory.

In the LEC method, 1×1017 ci-' or more, preferably,
It is necessary to add a neutral impurity of 1 x 1 x 1017 ci-' or more, but in the case of the horizontal boat method or the vertical Bridgman method, AJ! and In is 1 x 1017 to 1 x lo”
By adding impurities at a low concentration of cn-', it is possible to reduce dislocations in the GaAs single crystal. In addition, when epitaxial growth is performed on such a substrate, the impurity concentration (especially In)
If is ≦1×10 17 crM-', no misfit dislocations (lattice mismatch) occur.

Although the gallium arsenide crystal may have either n-type or p-type conductivity, it can also be made semi-insulating with a specific resistance of 10<7 >[Omega]C1 or more by adding Cr.

[Examples] Examples of the present invention will be described in detail below, but the present invention is not limited to these examples.

Seed crystal and Mf4 Ga 800g, AI9.7IIg
, I n55B, and a boat containing Si 250n+g as an additive to obtain an n-type conductive crystal was placed on one end of a quartz glass reaction tube, and A s on the other end.
After placing 870 g, the vacuum 11 of this quartz glass reaction tube was stopped.

The above reaction tube was installed in a double electric furnace, and the boat It! l
(high-temperature furnace) to 12,000℃ or higher, AsQl (low-temperature furnace)
After the GaAs synthesis reaction is completed, the temperature of the high-temperature furnace is further raised while keeping the temperature of the low-temperature furnace constant, and the seeded portion is heated to the melting point of GaAs of 1.
The electric furnace is adjusted to 238°C so that there are six temperature gradients (approximately 1 data/cn) so that the temperature on the boat body side is higher. In this way, after melting part of the seed crystal, the temperature gradient mentioned above was maintained: j, ma, 1 deg
After the temperature was lowered at a rate of 30 deg/h to solidify the whole, the settings of the electric furnace were adjusted again so that the temperature gradient of the boat installation part in the electric furnace was zero, and the temperature was lowered to 700°C at a rate of 30 deg/h. 70
After being maintained at 0° C. for about 150 hours, it was cooled to room temperature at 100 dco/h and the crystals were taken out.

A GaAs single crystal of about 16,000 crystals was obtained by the above method.

Next, this single crystal was cut to a thickness of approximately 111 with a Miller index (100), one side was mirror polished, and then etched with molten potassium hydroxide (KOH) to increase the density (EPD) to edge pitch 1. When measured, as shown in Figure 1,
It was found that it was a ready crystal with no dislocations in the center and a low dislocation density (average EPD of 120 c'2) with EPD≦500 cn-'' in the peripheral areas.

In addition, the above 41 crystal has a carrier concentration of 1xlO”C11
-'~3x10'''C1-', and it was found that there was no problem with electrical characteristics.Specifically, solidification rate g of single crystal =
As a result of measuring the concentration of In and A1 at 0.1 with a glow discharge material analyzer (GDMS), N , , =
IX 1017C11-'-N Al = IX
It was confirmed that lattice mismatch between the substrate and the epitaxial layer does not occur in a liquid phase epitaxial (LPE) substrate using a substrate.

Note that similar effects can be obtained even in the case of the vertical Bridgman method.

[Effects of the Invention] As described above, according to the present invention, it is possible to reduce dislocations in a GaAs single crystal by adding impurities at low concentrations of 1 xlo" to 1 xlo"cll-' of All and In, respectively. can. Further, when epitaxial growth is performed on such a substrate, no lattice mismatch occurs at all.

[Brief explanation of the drawing]

FIG. 1 is a wafer in-plane dislocation density distribution diagram of a crystal obtained by the method of the present invention using the boat method.

Claims (1)

[Claims] 1. When producing gallium arsenide single crystals by the horizontal boat method or the vertical Bridgman method, both aluminum and indium, which are neutral impurities, are mixed at 1×10^1^7 to 1×
A method for producing a gallium arsenide single crystal, characterized in that gallium arsenide is added at a concentration of 10^1^8 cm^-^3.