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

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