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HL: Fachverband Halbleiterphysik

HL 99: Electronic structure theory

HL 99.7: Vortrag

Donnerstag, 3. April 2014, 16:30–16:45, POT 151

Wavefunction localisation and acceptor ionisation in Ga_1−xMn_xAs, an electronic structure perspective — •Jerome Jackson and Gabriel Bester — Max-Planck-Institut für Festkörperforschung, Heisenbergstraße 1, 70569 Stuttgart, Germany.

The Mn acceptor level in GaMnAs, although it has a binding energy well beyond that of a simple effective-mass impurity, is nevertheless weakly localized and has considerable valence band character. We discuss critically the ability of density functional theory methods to correctly reproduce the acceptor level localization, in direct contrast to clear experimental evidence (photoluminescence and tunneling experiments) for discrete Mn acceptor levels in the dilute limit. Using a non-selfconsistent wavefunction based approach, relying upon the essentially shortranged nature of the Mn defect potential, we are able to study the localization behavior of the acceptor wavefunction and apply corrections (in agreement with previous tight binding results) which improve upon the density functional description. We identify the principle problem with such calculations as being a poor description of the important sp−d coupling, distinct from the problem of the deep Mn d state position. By calculating the screened Coulomb integrals between the defect states and the host bands and using a configuration-interaction method we are able to explicitly model the acceptor level ionization, illustrating the fundamentally many-body nature of such processes.