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HL: Fachverband Halbleiterphysik

HL 9: Poster 1

HL 9.35: Poster

Montag, 23. März 2009, 14:30–17:00, P2

Hole Density in (Ga,Mn)As layers grown on (001), (110) and (311) GaAs Substrates — •Michael Hirmer, Michael Mayr, Tobias Korn, Ursula Wurstbauer, Martin Utz, Stefanie Heydrich, Dieter Schuh, Werner Wegscheider, and Christian Schüller — Universität Regensburg, Universitätsstraße 31, 93053 Regensburg, Germany

The dilute magnetic semiconductor (DMS) Ga_1−xMn_xAs is a very promising candidate for building spintronic devices, due to theoretically predicted room temperature ferromagnetism. Since the ferromagnetism of this Zener-like DMS is hole-mediated, the ferromagnetic transition temperature T_C corresponds to T_C α x_effp^1/3 (x_eff: effective Mn concentration, p: carrier density). We present a detailed study of carrier concentrations, determined by Hall measurements and Raman scattering on thin Ga_1−xMn_xAs films. The films were grown on (001), (311) and (110) semi-insulating GaAs substrates with layer thicknesses ranging from 5 to 300 nm and Mn contents of 6% using low temperature molecular beam epitaxy. Hole concentrations in the range of 10²⁰ cm⁻³ were found with highest values for (001), in correspondence with the measured T_C values. Samples with higher T_C show a contribution of side jump to AHE, only. Measurements before and after annealing suggest that the AHE is not caused by scattering processes, only, consist with theoretically predicted intrinsic contributions. Therefore, we used Raman scattering intensity analysis of the uncoupled LO and the coupled plasmon LO phonon mode to determine p, independent of transport measurements, before and after annealing.