RHEED STUDIES OF MOMBE GROWTH USING TMGA OR TEGA WITH AS2

MOMBE and CBE growth has until recently been based on largely empirical studies of the epitaxial process. We have used reflection high energy electron diffraction (RHEED), previously applied to the study of MBE, to study the growth GaAs using TMGa and As2. In this work we have extended our previous studies to include a detailed study of the effect of AS2 flux on growth rate and to compare data on singular and vicinal plane surfaces cut off orientation in two orthogonal {110} directions. Clear evidence for site blocking mechanisms is observed together with an indication that the concentration of elemental Ga present on the surface during growth is negligible even under conditions where the arrival rate of TMGa exceeds that of As2. We have compared this behaviour with that observed using TEGa and As2 under identical conditions. Using TEGa a conversion from a (2 x 4) to (4 x 2) reconstructed surface is observed under As deficient conditions indicating the presence of elemental Ga on the surface. This is accompanied by an abrupt change in growth rate similar to that seen in MBE.