Behavior of SiNx films as masks for Zn diffusion

The detailed behavior of SiNx films as masks for Zn diffusion into GaAs at both low and high temperatures has been investigated. It is found that the film behavior as a mask is a function of the refractive index of the SiNx mask film and that a film with index n=2.06 shows optimum performance at both 650 and 950 °C. The experimental results suggest that the film with n=2.06 is nearly stoichiometric. Possible reasons for this optimized masking behavior are discussed.