Fundamental Study of GaN-on-Si Hetero-Epitaxial Substrate for Earth Environmental Preservation

GaN和AlGaN化合物是唯一有前途的大功率器件和紫外光电子器件材料。蓝宝石和SiC衬底上的GaN基光电子器件已经得到了广泛的应用。另一方面，尽管Si具有许多优点，如高质量、低成本、导电性可控以及与Si-ULSI技术相结合的应用的有效性，但在硅衬底上的GaN基器件还没有被执行。由于GaN层与Si衬底之间的异质界面容易发生相互作用，在Si衬底上外延GaN很难获得高质量的GaN外延层。本工作采用NH_3气体源分子束外延技术，在Si（111）和Si（100）衬底上，以0.6μm厚的γ-Al_2O_3外延层作为中间层，利用原位反射高能电子衍射系统研究了GaN外延层的生长行为。发现γ-Al_2O_3层能有效地抑制Si衬底表面的氮化。在γ-Al_2O_3Si（100）衬底上外延生长了立方相GaN，在γ-Al_2O_3Si（100）衬底上外延生长了表面平整的六方GaN层

The GaN and compounds of AlGaN are only promising materials for high-power devices and opto-electronic devices in the ultra violet-wavelength region. Many GaN-based opto-electronic devices are demonstrated on sapphire and SiC substrate. On the other hand, the GaN-based devices on silicon substrate have not been performed regardless of many advantages of Si such as high quality, low cost, controllability of the conductivity and effectiveness for the application combined with Si-ULSI technology. It is hard to obtain high quality GaN epilayer on Si because it is easy to occur the interaction at the hetero-interface between GaN layer and Si substrate. Therfore, it has been expected to grow a device-quality GaN epilayer on Si using an appropriate buffer layer.In the present work, we have investigated the growth behavior of GaN epilayer on Si(111) and Si(100)substrates coverd with 0.6μm thick γ-Al_2O_3 epitaxial layer as an intermediate layer by NH3 gas source molecular beam epitaxy with in-situ reflection high energy electron diffraction system. It is found that the nitridation of the surface of the Si substrate is effectively suppressed with γ-Al_2O_3layer. The GaN under cubic phase was epitaxially re-grown on γ-Al_2O_3Si(100) substrate and hexagonal GaN layer with flat surface on γ-Al_2O_3Si(100)