DEPSCOR 95. Molecular Beam Epitaxy of Non-Stoichiometric III-V compounds: Theoretical Modeling and Simulation

摘要

Surface dynamics dominate the incorporation and segregation of atoms in the molecular beam epitaxy (MBE) of compound semiconductors. A rate equation model is proposed which includes the presence and dynamics of a physisorbed surface layer containing atoms riding the growth surface. The PA layer dictates the incorporation and concentration of various atomic species, such as AS(+)(sub Ga) and As(sup 0)(sub Ga) in low temperature GaAs MBE and In in InGaAs MBE growth. Additionally, it influences the RHEED oscillations (ROs) behavior. The model results for the dependence of As(+)(sub Ga) and As(sup 0)(sub Ga) concentrations on beam equivalent pressure (BEP) and growth temperature are in good agreement with experimental data. Using the same kinetic model for the temporal behavior of the surface, the contribution of the PA layer to the RHEED intensity is computed based on kinematical theory of electron diffraction. The experimental observation of the ROs during growth at high and low temperatures with no ROs in the intermediate temperature range of 300-400 deg C is in good agreement with our model results. The same model is extended to investigate the segregation of In in InGaAs at temperatures in the range of 500-700 deg C for As (both dimer and tetramer) BEPs of 17 and 36. The model results of In incorporation rate versus growth temperature, segregation coefficient versus growth temperature and desorption rate versus time, are in excellent agreement with various results for a wide range of growth conditions reported in the literature. Activation energies for the various surface processes are in good agreement with literature.