Photoreflectance characterization of GaAs as a function of temperature, carrier concentration, and near‐surface electric field

Previous measurements of the photoreflectance line shape of GaAs at the E1 transition (2.9 eV) were extended. This study covers the combined effect of temperature and carrier concentration along with a discussion of the effect of the electric field intensity and the field inhomogeneity within a depth of 20 nm from the surface. A systematic study of changes in the line shape of the above band gap transition, E1 as a function of temperature (80–400 K) and carrier concentration (CC) (2–200×1016 cm−3) is presented and a model of the effect is discussed. It was found that as the carrier concentration increases beyond 1×1017 cm−3, the line shape changes in phase and in broadening in a characteristic way which depends on CC and temperature. A simple correlation is established between both the broadening and the line shape rotation as a function of temperature and CC. Using the Schottky relation and Fermi‐level pinning, the observed effect qualitatively was explained. Also the effect of near‐surface electric fiel...