Photoreflectance characterization of surface Fermi level in ashyphen;grown GaAs(100)

摘要

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 Verbar;Dgr;R/RVerbar; is proportional to a modulating photovoltageVmgenerated by a modulation light irradiation. To modify the surface potential, the sample was irradiated by a third perturbing light, i.e., a continuous bias lightPb, together with the modulation light. The modulation light power dependence of Verbar;Dgr;R/RVerbar; is extremely sensitive to bias light intensity, surface Fermi level, and temperature. From the analysis of the temperature dependence of Verbar;Dgr;R/RVerbar; on modulationhyphen;light power, the surface Fermi level of 0.47plusmn;0.09 eV below the conduction band was determined for a molecular beam epitaxiallyhyphen;grown GaAs(100).