Electronic structure of Ga_1-xMn_xAs analyzed according to hole-concentration-dependent measurements

We study the effects of variable hole concentration on the transport, thermoelectric, and magnetic properties of Ga_1-xMn_xAs. The hole concentration in samples with fixed Mn content has been varied using high energy particle irradiation, which introduces donorlike defects that compensate Mn acceptors without changing the concentration of localized Mn spins. As expected, a decrease of the hole concentration results in a reduction of the Curie temperature and an increase in electrical resistivity and thermoelectric power. The mobility and thermopower data are then analyzed in terms of models based on free holes in the valence band and holes localized in a Mn impurity band. The energetic structure of the impurity band is described by the valence-band anticrossing model. We show that the electronic structure provided by the impurity band model is consistent with the experimental results. © 2010 The American Physical Society.