GB1005789A - Improvements in or relating to methods of producing monocrystals - Google Patents

Abstract

Single crystals of either elements or compounds are prepared by subjecting the element or compound or mixture of elements to a heat treatment in the presence of a transport gas, whereby at a first place in a reaction space with a temperature gradient one of the starting materials reacts with the transport gas to form a gaseous compound and at a second place a monocrystal is deposited and the transport gas released, the vessel in which the reaction is performed being displaced relative to the temperature gradient so that as the crystal grows the temperature conditions at the point of deposition are maintained substantially constant. Single crystals of silicon or the following binary compounds: phosphides, arsenides, antimonides and nitrides, e.g. GaP, AlP, AlAs and cadmium arsenide; sulphides, selenides, tellurides, e.g. zinc sulphide and cadmium sulphide; AIIIBV compounds where AIII is an element of the third main group (B, Al, Ga, In) and Bv is an element of the fifth main group (N, P, As, Sb) may be prepared. Binary peritectic compounds and binary compounds which undergo a phase change at a conversion temperature, e.g. Cd3As2 may also be obtained. The transport gas may be a halogen or halide. During deposition an impurity may be incorporated into the monocrystal by adding the impurity, e.g. chlorine, arsenic, sulphur, zinc or gallium to the vessel. In an Example: (1) a GaP crystal is grown from GaP powder using iodine as transport gas, and in a modification a GaP crystal containing thallium impurity is made from GaP produced by heating thallium alloyed gallium and hydrogen phosphide.