Influence of nitrogen incorporation on structural, electronic and magnetic properties of Ga1-xMnxAs

For spin injection, detection and manipulation, diluted magnetic semiconductors are interesting materials. GaMnAs is one of these candidates, though the ferromagnetism occurs only at temperatures below 110 K. In order to possibly increase the Curie temperature, nitride based III-V semiconductors have been proposed. Here, we report results on the structural, magnetic and electronic properties of Ga1-xMnxNyAs1-y. In GaMnNAs, the valence band maximum is supposed to increase in energy with N concentration, and since Mn is a relative deep acceptor with an activation energy of 110 meV, this would lead to a reduction of the activation energy and hence to a higher doping level. GaMnNAs thin films have been grown by low-temperature molecular-beam epitaxy. We present experimental data on the transport properties of this compound, indicating that it is ferromagnetic at low nitrogen concentrations. Samples with higher N concentration show a decrease of the Curie temperature or even no ferromagnetism at all and a high ohmic resistance compared to GaMnAs reference layers. This is most probably due to a compensation of the holes, which are needed for the ferromagnetic coupling. (C) 2002 Published by Elsevier Science Ltd.