Determination of surface state density for GaAs and InAlAs by room temperature photoreflectance

Room temperature photoreflectance (PR) was used to investigate the surface state densities of GaAs and In0.52Al0.48As surface intrinsic-n(+) structure s. The built-in electric field and thus the surface barrier height are eval uated using the observed Franz-Keldysh oscillations in the PR spectra. Base d on the thermionic emission theory and current-transport theory, the surfa ce state density as well as the pinning position of the Fermi level can be determined from the dependence of the surface barrier height on the pump be am intensity. Even though this method is significantly simpler, easier to p erform, and time efficient compared with other approaches, the results obta ined agree with the literature. (C) 1999 American Institute of Physics. [S0 021-8979(99)03815-3].