A model for the dynamics of island growth during deposition of compound semiconductors

Abstract

A model has been developed that describes the microscopic phenomena which take place during epitaxial growth of compound semiconductors. The treatment includes the many elementary processes that can occur at each of the different types of surface sites available. Rate constants for these processes are determined using statistical mechanics and transition state theory. Many of the reactions are fast and reversible and, therefore, a new procedure has been used to account for these steps in an efficient yet realistic manner. The utility of the approach is illustrated by considering homoepitaxial chemical vapor deposition of GaAs from Ga(CH 3) 3 and AsH 3 on a defect-free (111)Ga surface. For the operating conditions considered, triangular islands are formed because the steps leading to generation of kink sites are more difficult than those that propagate the kink sites. The agreement between this result and experimental observations, albeit on a larger scale, suggests that these factors also influence the overall deposit morphology. In addition, the calculations show that growth is autocatalytic with respect to ledge sites. One consequence of this factor, coupled with the probabilistic nature of complex formation at ledge sites, is that islands of equal size do not grow at the same rate. Sensitivity studies have been performed to assess the impact of simulation parameters and uncertainties in the rate constants on the theoretical predictions.