Electron traps in AlGaAs grown by molecularhyphen;beam epitaxy

摘要

Using deephyphen;level transient capacitance spectroscopy we have investigated deep electron traps innhyphen;AlGaAs grown by molecularhyphen;beam epitaxy (MBE). The thermal activation energies of seven traps, labeled ME1ndash;ME7, observed in this study increase with increasing Al content(x) up to the directhyphen;indirect crossover point (xsim;0.42), but show only a small change with further increases in Al content. Traps ME4ndash;ME7 are dominant in samples withxle;0.2. Traps ME4ndash;ME6 strongly depend on the growth ambient. The concentration of ME7 is almost independent of the ambient in the growth chamber but decreases rapidly with increasing growth temperature. ME7 is a native defect and can almost certainly be identified with the trap EL2 observed in bulk and vaporhyphen;phase epitaxially grown GaAs. Traps ME4ndash;ME6 are probably formed by impurities involving oxygen such as CO, H2O, and AsO in the growth ambient. All of the traps, ME5ndash;ME7 are clearly responsible for a decrease in the photoluminescence intensity of MBE grown AlGaAs.