Regensburg 2007 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 46: Poster 2
HL 46.36: Poster
Donnerstag, 29. März 2007, 15:00–17:30, Poster A
Post growth annealing beahaviour of GaMnAs grown on (001), (311) and (110) GaAs substrates — •Hirmer Michael, Ursula Wurstbauer, Dieter Schuh, and Werner Wegscheider — Universität Regensburg
We report a detailed study of post growth annealing experiments of thin GaMnAs films grown by low temperature molecular beam epitaxy (LT-MBE) on (001), (311) and (110) semi-insulating GaAs substrates with layer thickness ranging from 5 nm to 300 nm. Since the ferromagnetism of this zener-like diluted magnetic semiconductor is hole mediated, the ferromagnetic transition temperature TC can be increased corresponding to TC xeffp1/3 (xeff: effective Mn concentration, p: carrier density) by post growth annealing. This reduces the Mn-interstitial lattice defects, which act as a double donor. We have increased TC in first annealing experiments at about 190∘C for 100h in air from 85K to 150K for layers grown on (001) GaAs, from 75K to 110K for layers on (311)A and from 55K to 89K for layers on (110) oriented substrates [1]. In these experiments, TC was determined by temperature dependent sheet resistivity measurements and the carrier density by measurements of the anomalous Hall Effect. To further improve the annealing process and to find the optimal annealing parameters (temperature, time, environment...) dependent on Mn concentration, layer thickness and growth direction we in situ monitor the sheet resistivity during the annealing process. We acknowledge the support by the DFG via SFB 689. [1] U. Wurstbauer, M. Sperl, D. Schuh, G. Bayreuther, J. Sadowski, W. Wegscheider, accepted to JCG