STOICHIOMETRIC LOW-TEMPERATURE (SLT) GAAS AND ALGAAS 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 (MBE) growth conditions, u sually results in a massive incorporation of excess As in the lattice which then totally dominates the electrical and optical characteristic s of the as-grown material resulting in almost electrically and optica lly inactive material (or at least defects controlled). In this review new phenomena associated with the growth of GaAs and AlGaAs at 250 de grees C are reported and data on highly electrically and optically act ive doped material are shown. The electro-optical properties of LT-GaA s are literally indistinguishable fi-om material grown at 580 degrees C. By careful control of the growth conditions, and hence stoichiometr y 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 L T-GaAs, can be achieved, therefore demonstrating that high quality GaA s and AlGaAs can in effect be epitaxially grown at very low temperatur es. Such materials are termed Stoichiometric Low Temperature (SLT) sem iconductors to emphasise the profound role of the latter in controllin g the electrooptical properties of the III-V compounds.