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-degre es-C, under standard molecular beam epitaxy growth conditions usually results in a massive incorporation of excess As in the lattice which t hen totally dominates the electrical and optical characteristics of th e as grown material resulting in almost electrically and optically ina ctive material (or at least defects controlled). We report on new phen omena 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 mate rial grown at 580-degrees-C. By careful control of the growth conditio ns, 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 c an 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.