Photoreflectance of GaAs and Ga0.82Al0.18As at elevated temperatures up to 600 °C

Abstract

We report a modulation spectroscopy experiment on GaAs and Ga_0.82Al_0.18As at elevated temperatures. Using the contactless electromodulation method of photoreflectance, the direct gaps (E₀) of these materials have been observed from 77 K to 600 °C. The latter temperature is comparable to molecular beam expitaxy, metalorganic chemical vapor deposition, growth temperatures, etc. Our results are at the highest temperature yet reported for E₀ (GaAs) in a reflectance experiment and the first observation of E₀ (Ga_1−xAl_xAs) at elevated temperatures. From the latter, the Varshni coefficients [Physica 3 4, 149 (1967)] for Ga_0.82Al_0.18As were determined.