INFRARED STUDIES OF BE-DOPED GAAS GROWN BY MOLECULAR-BEAM EPITAXY AT LOW-TEMPERATURES

Samples of molecular beam epitaxial GaAs grown at low temperatures dop ed with Be defects are studied as a function of growth temperature (T- G) by measuring their localized vibrational modes at 77K using BOMEM F ourier transform infrared spectrometer. Localized vibrational modes of Be-9(Ga) in samples grown at T-G>350 degrees C have been identified a t 482 cm(-1). Secondary ion mass spectroscopy measurements show that t he densities of Be defects remain approximately constant as T-G is low ered, however, additional structure in the Be-9(Ga) localized vibratio nal mode is observed. Calculations based on Green's function theory su ggest that the additional structure in Be-doped LT GaAs can best be ex plained in terms of a complex center [Be-9(Ga)-As-Ga] involving an int rinsic defect.