Dresden 2009 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 9: Poster 1
HL 9.117: Poster
Montag, 23. März 2009, 14:30–17:00, P2
Electrical measurement of the effective density of states in (Ga,Mn)As — •D. Neumaier1, A. Vogl1, U. Wurstbauer2, M. Utz1, W. Wegscheider1, and D. Weiss1 — 1Universität Regensburg — 2Universität Hamburg
In ferromagnetic (Ga,Mn)As the conductivity σ decreases with decreasing temperature below 10 K. Preliminary experiments have shown that enhanced electron-electron interaction (EEI) [1] is the origin of this conductivity decrease [2]. The size of the conductivity correction due to EEI is depending on the diffusion constant D. Hence a detailed analysis of the conductivity correction provides experimental access to the diffusion constant. The diffusion constant is connected to the effective density of states at Fermi’s energy N(EF) by Einstein’s relation: σ=e2N(EF)D. For (Ga,Mn)As it is still an open issue whether Fermi’s energy is in the valence band or in a detached impurity band [3]. Here we present measurements of the conductivity correction in quasi 1D and quasi 3D (Ga,Mn)As, as well as in the crossover regime from quasi 2D to 1D, to get knowledge about the diffusion constant and the effective density of states. The measured values of N(EF) will be compared with recent theoretical calculations [4]. The good agreement shows, that the transport in (Ga,Mn)As can be described well within the picture, that Fermi’s energy is in the valence band.
[1] P. A. Lee and T. V. Ramakrishnan , Rev. Mod. Phys. 57, 287 (1985). [2] D. Neumaier et al., Phys. Rev. B 77, 041306(R) (2008). [3] T. Jungwirth et al., Phys. Rev. B 76, 125206 (2007). [4] M. Turek et al., Phys. Rev. B 78, 085211 (2008).