Shallow diffusion was improved by using a new spun-on source which was based upon Zn-doped alumina. In this case, the thermal expansion coefficients of the diffusion source and the semiconductor were better matched than when using Zn-doped silica films. As well as excellent mechanical stability of the spun-on films over a wide temperature range, the effect of mechanical stresses upon the diffusion process was effectively reduced.

M.C.Amann, G.Franz: Journal of Applied Physics, 1987, 62[4], 1541-3