Structural And Optical Characterization Of AlxGa1−xAs Grown At Low Temperatures By Organometallic Vapor Phase Epitaxy

We report on the low temperature growth of AlxGa1−xAs by conventional Organometallic Vapor Phase Epitaxy OMVPE for a substrate temperature of 500°C and V/III ratios extending to subunity. Optical, structural and electrical qualities are assessed with double crystal X-ray diffraction, Nomarski and atomic force microscopy, 1.6K and 300K photoluminescence, Rutherford backscattering and Hall measurements. Although our low temperature grown films are of good structural and optical quality, they exhibit high background p-doping (carbon) and high levels of hydrogen passivation. A method for extracting the carbon doping levels from lattice contraction measurements is suggested. The dependence of layer composition, free carrier concentration and hydrogen passivation on growth parameters are investigated. Moreover, the effects of post-growth annealing on free carrier concentration, lattice parameter and optical qualities are studied. The influence on the bandgap of bandtail states and compressive strain due to carbon are compared.