CDT Compound Semiconductor Physics (PhD Progression 1+3)

卡迪夫的团队成功地在(111)硅(Si)衬底上生长了外延氮化镓(GaN)层。这可能是能够将用于光子学的发光二极管(LED)集成到标准硅工艺技术生产线上的一种解决方案。关键问题是GaN的-17%拉伸应变导致晶片开裂，以及由于GaN和Si之间的失配和热膨胀失配而产生密集的失配位错网络，以及为器件操作形成良好的欧姆电接触。在这项结合电子显微镜和电子能谱的研究中，将研究探索和减少晶格应变的各种方法，其中一个关键问题是电触点的退火是否以及在多大程度上提高了GaN层的应变弛豫。B项目中将使用能量色散X射线光谱(EDX)、EDX映射、电子能量损失光谱(EELS)和能量损失近边缘光谱(ELNES)和能量过滤成像(EFTEM)来研究横截面上的局部化学，测量原子尺度的互扩散，并优化需要沉积后退火的电接触多层膜的质量。

The team in Cardiff successful grows epitaxial gallium nitride (GaN) layers on (111) silicon (Si) substrates. This may be one solution to enable integration of light emitting diodes (LEDs) for photonics onto standard Si process technology production lines. Key issues are wafer cracking due to -17% tensile strain of the GaN and the generation of dense misfit dislocation networks due to the misfit and the thermal expansion mismatch between GaN and Si and also the formation of good ohmic electrical contacts for device operation. Various methods to explore and reduce lattice strain will be investigated in this combined electron microscopy and electron spectroscopy study where one key question to answer is whether and to what degree the anneal of the electrical contacts enhances strain relaxation in the GaN layers underneath.Energy-dispersive X-ray spectroscopy (EDX), EDX mapping, electron energy-loss spectroscopy (EELS) with energy-loss near-edge spectroscopy (ELNES) and energy-filtered imaging (EFTEM) will be used in project B to study the local chemistry in cross-section, to measure interdiffusion at the atomic scale and optimise the quality of the electrical contact multilayers that require annealing after deposition.