[16a-503-1~12] 15.4 III-V-group nitride crystals

△ [16a-503-12] Theoretical proposal of power devices based on SiC and
AlN/GaN short period super lattices

〇Eiji Kojima¹, Kenta Chokawa¹, Hiroki Shirakawa¹, Masaaki Araidai^1,2, Yasuhiro Ebihara³, Takashi Kanemura³, Shoichi Onda^2,3, Kenji Shiraishi^1,2 (1.Graduate School of Engineering, Nagoya University, 2.Institute of Materials and System for Sustainability, Nagoya University, 3.Denso Corporation)

Keywords:Powerdevice, SiC, GaN

There has been a growing interest in both silicon carbide (SiC) and gallium nitride (Al_xGa_1-xN) as next-generation power conversion devices because of their superior material properties such as larger band gap, higher saturation velocity and higher breakdown voltage than silicon (Si). We are attempting to develop a new type of vertical MOSFET with SiC/Al_xGa_1-xN heterojunction as a next-generation power conversion device. One of the prerequisites for the realization of the vertical MOSFET is that the conduction-band offset (CBO) of SiC/Al_xGa_1-xN interface is small enough to eliminate the interface scattering when electrons go across the interface. Therefore, we calculated the CBO of SiC/Al_xGa_1-xN interface by the first-principles calculation code based on the density-functional theory, and we clarified the condition that the CBO became zero. We made 4H-SiC/Al_xGa_1-xN 2x2 interfaces mimicked by the superlattice models. However, the models have saw-toothed electric fields perpendicular to the interfaces owing to the superlattice structure. We found that the unfavorable fields were removed by taking into account the electron-counting model of covalent bond and then the CBO were evaluated successfully. In addition, we calculated the CBO of SiC/Al_xGa_1-xN with AlN/GaN short period superlattice structures proposed by Suda group. As a result, we observed that the offset value decreases with increase in Al content and the Al content where the CBO becomes zero is about 75%. Therefore, 4H-SiC/Al_0.75Ga_0.25N interface is one of the most promising candidates for the vertical MOSFET in future power conversion devices.