ε-Ga2O3: A Promising Candidate for High-Electron-Mobility Transistors
Jin Wang, Hui Guo, Chengzhang Zhu, Qing Cai, Guofeng Yang, Junjun Xue, Dunjun Chen, Yi Tong, Bin Liu, Hai Lu, Rong Zhang, Youdou Zheng
Abstract
We predict spontaneous polarization of ε-Ga <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> can achieve a high density of 1014 cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-2</sup> two-dimensional electron gas (2DEG) at the interface of ε-Ga <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> and m-AlN (m-GaN) without doping. Based on the accurately calculated bandgap alignment of ε-Ga <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> , AlN and GaN, we find that the critical thickness of the ε-Ga2O3 to form a mobile 2DEG at the interface on m-AlN and m-GaN substrates is around 1.8 nm, which is much thinner than AlGaN due to its large potential shift. The depletion mode high-electron-mobility transistors (HEMTs) based on ε-Ga <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> are also investigated. The results show that the saturation currents of ε-Ga <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> HEMTs devices are much larger than that of typical AlGaN HEMTs. For the emerging problem of large leakage current from ε-Ga <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> HEMTs device, we present a novel method that can significantly suppress the off-state leakage current of the device by growing an ultrathin AlGaN layer on the top surface of ε-Ga <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> . Therefore, our results can provide a theoretical basis for the potential applications of ε-Ga <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> in fabricating HEMTs for high-power and high-frequency applications.