SELECTIVE GROWTH OF III-NITRIDE MICROSTRUCTURES ON SILICON SUBSTRATE

采用III族氮化物金属有机气相外延（MOVPE）中的选择性区域生长方法（SAG），开发了在特定晶面上生长GaN/AlGaN和InGaN/GaN微纳米异质结构。研究发现硅衬底上AlN中间层的形成过程和性能对于后续III族氮化物的生长具有重要作用。我们已经获得了直径为 200-500 微米、无裂纹的单晶。人们发现化学物质在气相和表面上的扩散过程对于确定合金的成分以及层厚度具有重要作用。详细讨论了Ga表面间扩散的作用。(1-101)GaN的生长是在7度偏向的(001)硅衬底上进行的。通过倾斜轴，我们首次实现了无裂纹且极其平坦的N面。由于平坦的界面，InGaN/GaN 双异质结构的光学特性表现出尖锐的边缘发射。使用该材料，我们实现了近带边缘波长 j 光损耗极低的光波导。利用飞秒光谱研究了激子的光谱和衰变过程，发现通过减小点/盘的尺寸可以降低激子的衰变速率。该方法被开发用于氢化物气相外延（HyPE）生长厚的GaN。使用厚的 MN 中间层，我们在 (111)Si 上实现了均匀的 23 微米厚的 GaN 层。

Adopting the selective area growth method (SAG) in the metal-organic vapor phase epitaxy (MOVPE) of III-nitrides, we have developed the growth of GaN/AlGaN and InGaN/GaN micro-and nano-heterostructure on specific crystal facets. It was found that the formation process and properties of the AlN intermediate layer on the silicon substrate has the essential role to the following growth of III-nitrides. We have achieved a single crystal free from cracks with the size of 200-500 micron across. The diffusion processes of the chemical species in the gas phase and on the surface were found to give an important role to determine the composition of the alloy as well as the layer thicknesses. The role of the inter-surface diffusion of Ga was discussed in detail.The growth of (1-101) GaN was performed on a 7 degree off oriented (001) silicon substrate. By declining the axis, we achieved crack free and extremely flat N-surface for the first time. Because of the flat interface, the optical properties of an InGaN/GaN double heterostructure exhibited a sharp edge emission. Using the material we achieve a optical waveguide with extremely low j optical loss for the near band edge wavelengths. Optical spectra and decay processes of excitons were investigated with femto-second spectroscopy and it was found that the decay rate is decreased by reducing the size of dot/disk.The method was developed to the growth of a thick GaN by hydride vapor phase epitaxy (HyPE). Using a thick MN intermediate layer, we achieved a uniform 23 micron thick GaN layer on (111)Si.