A long-term reliable spun-on source was developed for open-tube p+ diffusion into III/V compound semiconductors. The source consisted of an aqueous/alcoholic solution of zircon alcoholate, doped with zinc chloride. After spinning and drying in air at 300C, a glassy film of ZrO2:ZnO on the semiconductor surface acted as a solid-state source for subsequent diffusion. This solution exhibited an excellent long-term durability. Furthermore, the thermal expansion coefficient of zirconia was well matched to that of most III/V compound semiconductors and yielded very stable films, even at high temperatures. This permitted essentially stress-free diffusion. Diffusion into GaAs was carried out at temperatures ranging from 600 and 700C. The hole concentrations and diffusion coefficients which were obtained by using this source were rather close to those obtained by using other diffusion techniques. The simpler handling and long-term durability of zirconia-based solutions offered significant advantages over other p+-diffusion techniques which were used in the preparation of III/V compound semiconductors.

G.Franz, M.C.Amann: Journal of the Electrochemical Society, 1989, 136[8], 2410-3