Excitonic reflectance of GaAs crystals cleaved in liquid helium

Abstract

We report optical reflectance spectra near the $n=1$ excitonic resonance of GaAs. The experimental results from crystals cleaved in liquid helium and exposed to air exhibit noticeable changes of the line shape. Comparison with a model based on the adiabatic approximation indicates that line-shape distortions by surface electric fields are unavoidable for air-exposed GaAs surfaces.