Abstract: A surface (30) of a wafer of indium phosphide (22) is treated by first etching the surface (30) with an aqueous solution of nitric acid and ceric ammonium nitrate. A toughening solution of about 4 parts by volume of acetic acid, about 4 parts by volume nitric acid, and about 1 part by volume hydrobromic acid is prepared and mixed. The roughening solution is contacted to the etched surface (30) of the wafer of indium phosphide (22) for about 15 to about 30 seconds to roughen the surface of the indium phosphide. Reaction products may be removed from the surface in aqueous hydrofluoric solution, and metal may be deposited upon the toughened surface in a strongly adhering layer (28).