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

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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)