Reliable Spin-On Source for Acceptor Diffusion into III/V Compound Semiconductors

A long-term reliable spin-on source for open tube p⁺-diffusion into III/V compound semiconductors has been developed. This source consists of a water/alcoholic solution of zircon alcoholate doped with zinc chloride. After spinning and drying in air ambient at 300°C a glassy film of ZrO₂:ZnO on the semiconductor surface acts as solid-state source for the subsequent diffusion. Unlike state-of-the-art silica-based sources, this solution exhibits an excellent long-term durability. Furthermore, the thermal expansion coefficient of zirconia is well matched to that of most III/V compound semiconductors and yields very stable films even at high temperatures to permit essentially stress-free diffusion. Diffusion experiments into GaAs have been carried out in the temperature range between 600° and 700°C. The hole concentrations and diffusion coefficients obtained with this source are rather close to those obtained by other diffusion techniques. The simple handling and long-term durability of the zirconia-based solutions, however, represent essential advantages over other p⁺-diffusion techniques used in the technology of III/V compound semiconductors.