[23a-P06-1~28] 21 Joint Session K "Wide bandgap oxide semiconductor materials and devices"(Poster)

[23a-P06-3] Thermal Stability of β-Ga2O3(001) Surface and Its Application to Epitaxial Growth

〇Shohei Murakami¹, Yusuke Seki¹, Arifumi Okada¹, Kohei Kadono¹ (1.Kyoto. Inst. Tech)

Keywords:scanning probe microscope, gallium oxide, surface structure

Wide-gap semiconductor β-Ga2O3 is one of the candidate materials of power devices. However, it is hard to make this crystal p-type because of its electronic structure. One of the approaches to implement p-n junction based on β-Ga2O3 is heteroepitaxy using the material feasible to be p-type such as NiO. In order to suppress defects at the interface between the n-type β-Ga2O3 substrate and the p-type layer, understanding the initial growth stage with high resolution is important. Ideally, the substrate surface should have atomically flat terraces. Such surface can be achieved through thermal annealing. However, suitable annealing conditions for β-Ga2O3 substrates are different depending on the surface orientation. Here we investigated the annealing condition for β-Ga2O3(001) surface and its possibility of application for heteroepitaxy. We used β-Ga2O3(001) doped with Sn as substrates. After cutting and cleaning the specimens were annealed using an electric furnace in air. NiO layers were prepared via vacuum evaporation of Ni followed by oxidation and sol-gel method. The surface structures were observed via atomic force microscopy and scanning tunneling microscopy. The chemical compositions and electronic structures near the sample surfaces were investigated via X-ray photoelectron spectroscopy. The bulk properties were observed via optical absorption and emission spectroscopies. The suitable annealing temperature to prepare atomically flat (001) surface is higher than the case of (-201) and in many cases grains and/or islands remained on the terraces. The NiO deposited on the surface with very thin shows granular morphologies independent of the preparation methods.