An amorphous compound is changed to single crystal structure by heating at an elevated temperature in an inert atmosphere or in an atmosphere of a forming gas, the amorphous compound is composed of at least one Group III-A element of the Periodic Table and at least one Group V-A element, the amorphous compound having an excess over stoichiometric amount of at least one Group V-A element. The single crystal phase compound, intrinsically doped with at least one element from Group V-A, has the properties of high conductivity for a semiconductor without using any extrinsic dopant and a non-alloyed ohmic contact with a metal.