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The chalcopyrite alloy ZnxCd1−xSnP2 is a potentially use-ful electronic material. In addition to having effective masses lower than and energy gaps similar to its III-V compound analogs, this alloy can also be lattice matched to InP. We have used an open-tube, sliding-boat, liquid-phase system to grow ZnxCd1−xSnP2 epitaxially on InP sub-strates. Unintentionally-doped layers have electron con-centrations as high as 3 × 1019cm−3 with mobility values of about 2,000 cm2/V-sec. These mobility values are sub-stantially larger than have been obtained in the equivalent III-V materials at similar concentrations.

The distribution of impurities incorporated in epitaxial layers during their growth is determined by diffusion due to concentration gradients and by drift in the built-in electric field. This problem has been previously treated in the approximation that the impurities reach their equilibrium distribution during growth. We have extended this calculation to treat impurity drift and diffusion under non-equilibrium conditions, a situation much more characteristic of most realistic growth condi-tions. In the new calculation, the solution of the Shockley-Poisson problem is exact and the boundary con-dition at the growth interface is an approximation based on the electrostatics of surface states. The new calcu-lation also permits consideration of outdiffusion from the substrate, a phenomenon of technological significance. It is also capable of modeling variations of source im-purity concentration and growth rate during epitaxial growth. Calculations modeling n-type GaAs epitaxy of practical interest are presented.