A method is disclosed for preparing a surface of a Group III-Group V compound semiconductor for epitaxial deposition. The III-V semiconductor surface is treated with boron (B) at a temperature of between about 250° C. and about 350° C. A suitable form for supplying B for the surface treatment is diborane. The B treatment can be followed by epitaxial growth, for instance by a Group IV semiconductor, at temperatures similar to those of the B treatment. The method yields high quality heterojunction, suitable for fabricating a large variety of device structures.