Defect complexes in GaN - Preparation, characterisation and ab-initio modelling

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The properties of intrinsic defects are of huge importance for the function and fabrication of semiconductor devices. Despite the successful use of group-III nitrides in commercial devices, point defects in GaN are still not really understood. In this joint project involving both theory and experimental groups located at one site, we plan to investigate intrinsic defects and their complexes with dopants in GaN. Theoretically, different approaches based on as well as beyond DFT will be applied. Explicitly, we plan the use of selfinteraction corrected exchange-correlation functionals as well as quasi-particle calculations within the GW approximation to determine the defect properties accurately. By this, we will not only obtain a deeper understanding of the specific defects in GaN, but also gain experience in the application of such methodologies in electronic structure calculations. We plan to study GaN in both phases, the hexagonal as well as the cubic material. Intrinsic defects will be intentionally introduced by electron irradiation and by variations of the stoichiometry during growth. They will be characterised by electrical, optical and magnetic resonance measurements. By means of comparison with the defect signatures calculated for candidate modells, the defect structures will then be determined. Besides the better understanding of GaN defects from a scientific point of view, the proposed project aims at exploring possible pathways towards high-purity semi-insulating (HPSI) hexagonal and cubic GaN.