Stoichiometric Low Temperature (SLT) GaAs and AIGaAs grown by molecular beam epitaxy

The growth of GaAs at low temperatures (LT-GaAs) at or below 250°C, under standard Molecular Beam Epitaxy (MBE) 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 asgrown material resulting in almost electrically and optically inactive material (or at least defects controlled). In this review new phenomena associated with the growth of GaAs and AlGaAs at 250°C are reported and data on highly electrically and optically active doped material are shown. The electrooptical properties of LT-GaAs are literally indistinguishable from material grown at 580°C. By careful control of the growth conditions, and hence stoichiometry, material in which total defect concentrations of less than 10¹⁷ cm^-3, well below the huge 10²⁰cm^-3 that is normally obtained in LT-GaAs, can be achieved, therefore demonstrating that high quality GaAs and AlGaAs can in effect be epitaxially grown at very low temperatures. Such materials are termed Stoichiometric Low Temperature (SLT) semiconductors to emphasise the profound role of the latter in controlling the electrooptical properties of the III-V compounds.