In situ reflectance-difference spectroscopy of GaAs grown at low temperatures

We present the results of in situ reflectance-difference spectroscopy (RDS) investigations of GaAs grown by molecular beam epitaxy at low substrate te mperatures (LT-GaAs). The linear electro-optic (LEO) features in the vicini ty of the E-1 and E-1 + Delta(1) optical transitions are found to depend on growth temperature T-g and V:III flux ratio. The observed LEO amplitude wa s found to decrease linearly with the measured neutral As antisite point de fect concentration [As-Ga(0)], for growth temperatures 200 degrees C < T-g < 300 degrees C. This behavior relies on the influence of As antisite defec ts on the optical response of GaAs. The nonstoichiometry of LT-GaAs can be estimated in real time through the LEO amplitude vs [As-Ga(0)] relation. Th is makes RDS very attractive not only for ill situ growth control but also for real-time tuning of the electronic properties of LT-GaAs. [S0163-1829(9 9)51432-X].