Anomalous diffusion of Cd in InSb

Systematic studies of Cd diffusion into InSb were performed by a two-temperature zone method with InSb substrate and Cd source temperature controlled independently. Diffusion profiles were determined by C-V measurements and were found to be anomalous as in other III-V diffusion systems. The junction depth plotted against the square root of diffusion time was not a straight line through the origin, indicating that the standard interstitial-substitutional model and the conventional Boltzmann-Matano method can not be used to analyze the result. This non-linearity in Cd diffusion in In-Sb, predicted previously by Kolodny and Shappir, was confirmed experimentally in the present work. The X_j versus √t plot can be fitted rather nicely by a model similar to that proposed previously by assuming D(X, C) as functions of both diffusion depth and time. Furthermore, a modified Boltzmann-Matano method was used to deduce the diffusion coefficients and normalized diffusion curves of Cd into InSb were obtained.