Cubic Nitride Semiconductor Heterostructures and Their Application to Optical and Electronic Devices

本研究计画已证实立方相氮化物半导体及异质结构在实际元件应用上的可行性。对于GaAs衬底上的GaN薄膜，通过改进金属有机物气相外延（MOVPE）生长技术，包括采用GaN中间层和在生长过程中引入砷超压，获得了六方GaN含量小于1%的高质量立方GaN外延薄膜。高质量的立方GaN薄膜显示出高的发光光学性能，没有来自晶体缺陷的深能级发光。微观结构分析揭示了立方GaN薄膜中六方相产生的细节。Si掺杂已经成功地实现了高导电率的n型导电。当条纹取向沿着适当的晶体取向时，使用精细光刻条纹掩模图案的立方GaN膜的选择性区域生长给出了上级质量的立方GaN。立方GaN/GaAs异质界面的光电导和电反射的详细表征澄清了平行的导电路径的存在，由于特定的带线的异质结构。使用射频等离子体氮源的分子束外延（MBE）在GaAs上得到了立方GaN和InN薄膜，其质量与MOVPE生长的薄膜相当。这些结果显示了立方氮化物半导体实际应用的可能性。

This research project has demonstrated the feasibility of practical device application of cubic phase nitride semiconductors and heterostructures. As for the GaN thin films on GaAs substrates, high quality cubic GaN epitaxial films that contains hexagonal GaN less than 1 % have been attained by improvement of metal-organic vapor phase epitaxy (MOVPE) growth technique including adoption of GaN intermediate layers and arsenic overpressures in the growth process. High quality cubic GaN films showed a highly luminescent optical property without deep-level luminescence coming from crystal defects. Microscopic structural analyses revealed the details of hexagonal phase generation in cubic GaN films. Si doping has been successful to realize high-conductivity n-type electrical conduction. Selective-area growth of cubic GaN films using fine lithography stripe mask patterns has given a superior quality cubic GaN when the stripe orientation is along the proper crystal orientation. Detailed characterization of cubic GaN/GaAs heterointerface using photoconductivity and electroreflectance clarified the existence of parallel conduction path due to the specific band-line up of the heterostructure. Molecular-beam epitaxy (MBE) using rf-plasma nitrogen source gave cubic GaN and InN films on GaAs with comparable quality with MOVPE-grown films. These achievements shows a possibility of practical applications of cubic nitride semiconductors.