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

本征缺陷的性质对半导体器件的功能和制造具有重要意义。尽管第三族氮化物已经成功地应用于商业设备，但GaN中的点缺陷仍然没有真正被理解。在这个位于同一地点的理论和实验小组的联合项目中，我们计划研究GaN中的本征缺陷及其与掺杂的络合物。理论上，将采用基于DFT和超越DFT的不同方法。明确地说，我们计划在GW近似下使用自相互作用修正的交换关联泛函和准粒子计算来准确地确定缺陷性质。通过这种方法，我们不仅对GaN中的具体缺陷有了更深入的了解，而且也为这种方法在电子结构计算中的应用积累了经验。我们计划研究六方和立方两种相的GaN。电子辐照和生长过程中化学计量比的变化会有意引入本征缺陷。它们将通过电学、光学和磁共振测量来表征。通过与为候选模型计算的缺陷特征进行比较，然后将确定缺陷结构。除了从科学角度更好地了解GaN缺陷外，拟议的项目还旨在探索获得高纯度半绝缘(HPSI)六方和立方体GaN的可能途径。

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.