[15p-W8E_101-1~13] 13.3 Insulator technology

5:00 PM - 5:15 PM JST(8:00 AM - 8:15 AM UTC)

[15p-W8E_101-13] First-principles studies of hole traps at GaN–SiO₂ interface

〇Yuansheng Zhao^1,2,3, Kenji Shiraishi^1,4, Atsushi Oshiyama^1,4 (1.IMASS Nagoya Univ., 2.QUEMIX, Inc., 3.Univ. of Tokyo, 4.CIES Tohoku Univ.)

Keywords:

semiconductor,MOS,hole trap

GaN-based metal–oxide semiconductor field-effect transistors (MOSFETs) are promising for future power devices. However, the emergence of hole traps at the interface between GaN and gate oxides such as SiO₂ is one of the greatest obstacles to high-performance GaN MOSFETs. During the fabrication of GaN/SiO₂ MOS structure, a GaO_x layer with 1~2 nm thickness is commonly believed to spontaneously form at the interface. In this work, we have successfully forged realistic GaN/GaO_x/SiO₂ models for both c and m interfacial planes without any dangling bonds by melt-quench molecular dynamics simulations with machine-learned interatomic potential. The structures are then carefully optimized and investigated using density functional theory (DFT) with accurate HSE exchange-correlation functional. It is revealed that although dangling bonds are absent, when one electron is removed from the system, the hole can still be trapped at three types of positions: (1) 2 or 3-coordinated O atoms in GaO_x layer, (2) O atoms in Si–O–Ga structure, and (3) N atoms exactly at the interface. In all cases, upon hole trapping, the bond length at the center O/N atom increases significantly, raising electrostatic potential and causing an unoccupied electronic state to be raised to the GaN band gap. The thermodynamic transition level ε(+/0) for all the traps are found to be generally located at 0~1 eV above GaN valence band maximum. These results show that the hole traps at the interface are likely to be intrinsic to the GaO_x interfacial layer and might not be easily eliminated. We also discuss the possible mechanism of hole trap suppression by heavy Mg doping as found experimentally.