INFLUENCE OF HG PRESSURE ON DIFFUSION-COEFFICIENT OF AS IN HGCDTE

Arsenic diffusion coefficients were measured in HgCdTe at 350-degrees- C within the single phase field. The diffusion coefficients displayed a strong dependence on Hg pressure, increasing by more than 1 x 103 wi th decreasing Hg pressure. These measurements were performed by growin g As doped HgCdTe films by Hg-rich liquid phase epitaxy on undoped or In-doped base layers, where the growth temperature ranged between 330 and 350-degrees-C. Use of these low growth temperatures under Hg-rich conditions permitted attainment of virtual step profiles in As, with n egligible diffusion into the base layers. These provided ideal startin g points for subsequent diffusion anneals. Diffusion of arsenic under selected low Hg pressures was then employed to tune the positioning of the p/n junction for double layer heterojunction films, by locating i t ahead of the heterointerface. Formation of valence band barriers to the photogenerated minority carriers across the junction could thus be avoided. When on the other hand, diffusion experiments were performed under Hg saturated conditions, the heterointerface moved at a faster rate than the p/n junction, leading to the formation of valence band b arriers.