NONSTOICHIOMETRY AND DOPANTS RELATED PHENOMENA IN LOW-TEMPERATURE GAAS GROWN BY MOLECULAR-BEAM EPITAXY

The growth of GaAs at low temperatures (LT GaAs) at or below 250-degrees-C, under standard molecular beam epitaxy growth conditions usually results in a massive incorporation of excess As in the lattice which then totally dominates the electrical and optical characteristics of the as grown material resulting in almost electrically and optically inactive material (or at least defects controlled). We report on new phenomena associated with the growth of GaAs at 250-degrees-C and we show data on highly electrically active doped material. The electro-optical properties of this material are literally undistinguishable from material grown at 580-degrees-C. By careful control of the growth conditions, material in which total defect concentrations of less than 10(17) cm-3, well below the huge 10(20) cm-3 that is normally obtained in LT GaAs, can be achieved therefore demonstrating that high quality GaAs can in effect be grown at extremely low temperatures. The implications for such material are far reaching and these will be discussed in the light of these new results.