Low-temperature molecular beam epitaxy of GaAs: A theoretical investigation of antisite incorporation and reflection high-energy diffraction oscillations

Surface dynamics dominate the incorporation of charged, As-Ga(+), and neutr al, As-Ga(0), antisite arsenic, and the temporal variation of reflection hi gh-energy electron diffraction (RHEED) intensity in the low-temperature mol ecular beam epitaxy of (100) gallium arsenide (GaAs). A rate equation model is proposed which includes the presence and dynamics of a physisorbed arse nic (PA) layer riding the growth surface. The PA layer dictates the incorpo ration and concentration of As-Ga(+) and As-Ga(0). Additionally, it influen ces the RHEED oscillations (ROs) behavior and the RO's dependence on its co verage through its contribution to the reflected intensity. The model resul ts for the dependence of As-Ga(+) and As-Ga(0), concentrations on beam equi valent pressure (BEP) and growth temperature are in good agreement with exp erimental data. The experimental observations can be explained based on the saturation of the PA coverage at one monolayer and the competing rate proc esses such as the As-Ga incorporation into and evaporation from the crystal line surface. Using the same kinetic model for the temporal behavior of the surface, the contribution of the PA layer to the RHEED intensity is comput ed based on kinematical theory of electron diffraction. The experimental ob servation of the ROs during growth at high and low temperatures with no ROs in the intermediate temperature range of 300-450 degrees C is in good agre ement with our model results, At low temperatures, the surface is covered b y the PA layer whose step density depends on that of the subsurface crystal line GaAs. Thus, a temporal variation of the step density of subsurface cry stalline GaAs results in ROs, but with a different step height, that of the PA layer, of 2.48 Angstrom. At high temperatures, the crystalline GaAs is exposed to the RHEED beam due to the evaporation of the PA layer and the RO s appear due to periodic step-density oscillations with a step height of 1. 41 Angstrom, which is the Ga-As crystalline interplanar distance. At interm ediate temperatures, the surface is partially covered by the PA layer resul ting in RHEED reflection contributions from both surfaces covered by the PA layer and crystal. Due to the very different interplanar distances between the crystalline GaAs and the PA layers, complete destructive interference of the RHEED intensity results at a 0.5 surface coverage of the PA layer. T he RO dependence on the As BEP is also presented and discussed. (C) 1999 Am erican Vacuum Society. [S0734-211X(99)04103-7].