Growth dynamics and an order-disorder transition in epitaxial alloy semiconductors

A stochastic theory describing epitaxial growth dynamics in binary alloy systems has been proposed. Considering the ''atom correlation'' in surface adsorption and diffusion processes, the effective Ising Hamilton of binary elements and the stochastic differential equation (master equation) are combined in a unified manner. Monte-Carlo !MC) calculations made on the basis of the stochastic equation of a binary growing system have successfully revealed the growth dynamics and the evolution of short-range ordering (SRO) and long-range ordering (LRO) during the epitaxial processes. It has been discovered that the LRO parameter shows a peak at a certain temperature below the order-disorder transition temperature. The presence of the peak in the LRO parameter in the order-disorder transition is caused by the interplay of adsorption and diffusion processes involving atom correlation among the surface atoms. As an example, it is noted that the experimental data relating to LRO parameter variation as a function of the growth temperature in a (In,Ga)P pseudobinary alloy exhibits such an order-disorder transition, showing a peak in the LRO value just below the order-disorder transition temperature.