First-principles diffuse reflectance spectroscopy was used to monitor substrate temperature transients and epilayer absorption during low-temperature GaAs molecular-beam epitaxy. A significant increase in the sub-bandgap absorption from low-temperature GaAs was found. The magnitude of absorption at 1.2eV correlated well with the concentration of As antisite defects. The incorporation rate of As antisites appeared to be uniform in spite of a substrate temperature transient due to effusion-cell radiation heating. The results showed that diffuse reflectance spectroscopy could be used for both growth-temperature measurements and real-time nonstoichiometry monitoring.

In Situ Diffuse Reflectance Spectroscopy Investigation of Low-Temperature-Grown GaAs. R.Zhao, M.J.Cich, P.Specht, E.R.Weber: Applied Physics Letters, 2002, 80[12], 2060-2