Overcoming the compensation of acceptors in GaN:Mg by defect complex formation

What is it about?

GaN is a key material for solid state lighting and high-power microelectronics. The realization of p-type conductivity in GaN:Mg is crucial for devices, the understanding of which is poor in comparison with the advances in applications, despite many experimental and computational investigations.Here we show that the major compensating donor centers VN and Mgi in p-GaN:Mg can be neutralized by binding to multiple MgGa acceptors, forming two kinds of acceptor complexes represented by 4MgGa-VN and 3MgGa-Mgi, which have smaller hole localization energies and lower formation energies than isolated MgGa. We use embedded cluster techniques that give access to a common reference energy and avoid artefacts present in the routinely employed periodic supercell method, and the state of the art hybrid density functional theory to overcome the notoriously difficult problem of electron self-interaction which allows us to calculate accurate defect transition levels. Our results make a key contribution to understanding the origin of p-type conductivity in GaN:Mg, and help explain the different doping behavior in samples grown by different methods.

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