NUCLEATION AND GROWTH-KINETICS OF GAAS DURING MOLECULAR-BEAM EPITAXY

Nucleation and the subsequent growth kinetics of GaAs during molecular beam epitaxy were studied by the RHEED intensity oscillation method. From the oscillation curve profile within one period, the evolution of a new monolayer of coverage was extracted on the basis of a kinematic approach. A large metastability time interval at the initial stage of every monolayer growth was observed. During this time interval the solid phase is not formed on the surface until critical Ga supersaturation is reached. The value of the critical Ga supersaturation did not depend on the incident Ga flux, but it decreased with the temperature at T(S) > 560-degrees-C. Two other stages may be distinguished in the growth process. One of them corresponds to the growth of supercritical clusters by diffusion. At a final stage the crystallization rate reveals a universal behavior; it depends only on the surface fractional coverage but not on the temperature.