ADATOM DENSITIES ON GAAS - EVIDENCE FOR NEAR-EQUILIBRIUM GROWTH

We examine the equilibrium of a compound semiconductor surface under m olecular beam epitaxy (MBE) conditions, both theoretically and experim entally. For GaAs, the Ga chemical potential and adatom density depend sensitively on As pressure as well as temperature. Our results sugges t that MBE growth may take place under conditions much closer to equil ibrium than has been believed. We also show that standard one-componen t models cannot, even in principle, reproduce both the adatom density and its temperature dependence.