Photoreflectance (PR) spectroscopy has been used to study the surface Fermi level in GaAs by taking account of photovoltaic properties at the semiconductor surface. The PR signal amplitude ‖ΔR/R‖ is proportional to a modulating photovoltage Vm generated by a modulation light irradiation. To modify the surface potential, the sample was irradiated by a third perturbing light, i.e., a continuous bias light Pb, together with the modulation light. The modulation light power dependence of ‖ΔR/R‖ is extremely sensitive to bias light intensity, surface Fermi level, and temperature. From the analysis of the temperature dependence of ‖ΔR/R‖ on modulation-light power, the surface Fermi level of 0.47±0.09 eV below the conduction band was determined for a molecular beam epitaxially-grown GaAs(100).

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Photoreflectance (PR) signal of n-type GaAs grown by molecular-beam epitaxy has been systematically studied as a function of modulation frequency in the PR measurements. The trap activation energy obtained from analysis of the frequency response of PR signal with its temperature dependence is 0.34 eV. The dramatic change in the frequency response has been observed as a function of the modulation (ac) and bias (dc) light intensities. The theoretical analysis has been made by assuming a single level electron trapping model. The calculated result shows a good agreement with the experimental data. Furthermore, photoluminescence spectrum associated with the deep level of the molecular-beam-epitaxy-grown GaAs was measured and compared with the PR data.

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InxGa1−xAs films have been grown by molecular beam epitaxy on graphoepitaxially grown germanium films on nickel replica sheets fabricated from an anisotropic etched silicon (001) surface. The crystallographic and optical properties of the InxGa1−xAs films have been characterized. The crystallographic orientation of the heteroepitaxial InxGa1−xAs has a small deviation from the orientation of synthesized surface relief in the graphoepitaxial substrate. This deviation in the heteroepitaxial film is caused by misorientation of the crystallographic orientation during the graphoepitaxial growth of germanium. The energy gap of the InxGa1−xAs has also a slight deviation from the expected one. The mechanism and its evidence have been studied.