Preparation of III-V materials by reduction

DETAILED DESCRIPTION The following detailed description relates to a method of producing III-V compounds and solid solutions by the reduction of a salt.
The complex salt referred to herein comprises as a cation at least one element selected from a group consisting of gallium and indium, and a complex anion comprising oxygen and at least one element selected from the group consisting of antimony, arsenic, and phosphorus.
Examples of complex salts produced by coprecipitation from ammonia-containing solutions include M.
sub.
a (NH.
sub.
4).
sub.
b H.
sub.
c (XO.
sub.
4).
sub.
y, where M is indium and/or gallium, X is at least one of phosphorus, arsenic, or antimony, where a.
ltoreq.
y, and (b+c)/3=y-a.
We have discovered that such salts will reduce in hydrogen at an elevated temperature to form a III-V compound or solid solution.
Still other complex salts are possible.
An excess amount of one or more of the III-V elements may be mixed in with the reduced III-V material.
Steps can be taken to minimize the amount of excess material, as discussed below.
In practicing the present invention, the salt can be prepared in a number of ways from a number of different starting materials.
One method that has been found to yield good results in coprecipitation of the salt from a solution.
Both acidic and basic solutions have successfully been used for the coprecipitation.
Another preparation technique is freeze drying of the salt, details of which can be found in U.
S.
Pat.
No.
3,516,935, assigned to the same assignee as the present invention.
In practicing the present invention, an excess of the more volatile element, typically the group V element, can be maintained during the reduction process in order to obtain a stoichiometric proportion or other desired proportions of the elements.
This excess of the more volatile element can be obtained by providing an overpressure of the more volatile element in the reducing atmosphere.
The solid product obtained upon reduction is typically a powder, which may become slightly sintered during the reduction process