The open-tube diffusion of Zn into GaAs0.8P0.2, from a Zn-doped silica film, was investigated. Films of AlN or SiNx were used as annealing caps. The dependence of the diffusion depth upon the thickness of an AlN cap was found to differ from the dependence upon SiNx cap thickness. The selective masked diffusion of Zn, using an AlN mask, was also studied. It was found that the diffusion depth during selective masked diffusion depended upon both the AlN cap thickness and the AlN diffusion-mask thickness. The results suggested that the diffusion depth was not necessarily governed by either the cap thickness or the diffusion-mask thickness. The effect of film stress upon diffusion depth was therefore investigated, and it was noted that the diffusion depth scaled with the total film stress. It was concluded that the total film stress was the main factor which determined the diffusion depth under the present conditions.

M.Ogihara, M.Taninaka, Y.Nakamura: Journal of Applied Physics, 1996, 79[6], 2995-3002