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 so lid phase is not formed on the surface until critical Ga supersaturati on is reached. The value of the critical Ga supersaturation did not de pend 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 gr owth process. One of them corresponds to the growth of supercritical c lusters by diffusion. At a final stage the crystallization rate reveal s a universal behavior; it depends only on the surface fractional cove rage but not on the temperature.