Regensburg 2007 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 21: III-V semiconductors II
HL 21.8: Vortrag
Dienstag, 27. März 2007, 12:45–13:00, H17
GaMnAs grown on (001), (311) and (110) GaAs — •Ursula Wurstbauer, Dieter Schuh, and Werner Wegscheider — Universität Regensburg
In order to realize new spintronic devices based on Mn-doped GaAs heterostructures, one has to understand in detail and improve the properties in GaMnAs. For this reason, an accurate control of the effective Mn x concentration and the carrier density is necessary in this hole mediated ferromagnetic semiconductor GaMnAs. So far it is known, that these parameters critically depend on the incorporation of Mn atoms in the host lattice and on lattice defects, mainly As antisites and Mn interstitials, both acting as double donors, which are caused by the unavoidable low temperature MBE growth. In our experiments, we have grown GaMnAs layers on differently oriented GaAs substrates to compare the influence of growth and post-growth-treatment parameters on the Mn incorporation and, hence on TC. We obtain the carrier density p by measuring the anomalous Hall Effect and the concentration of As-antisites from the lattice constant of LT-GaAs layers by X-ray diffraction. Further we show, that by avoiding As-antisites with a low As4/Ga flux ratio and by reducing the Mn-interstitials by post growth annealing the carrier density and corresponding TC increases to 152K for layers grown on (001) GaAs, to 110K for layers on (311)A and 89K for layers on (110). In addition, the possibility to overgrow cleaved (110) surfaces with GaMnAs of a high quality enables the growth of more complicated heterostructures like magnetic bipolar heterojunctions. We acknowledge the support by the DFG via SFB 689.