ε-Ga2O3: A Promising Candidate for High-Electron-Mobility Transistors

We predict spontaneous polarization of ε-Ga ₂ O ₃ can achieve a high density of 1014 cm ^-2 two-dimensional electron gas (2DEG) at the interface of ε-Ga ₂ O ₃ and m-AlN (m-GaN) without doping. Based on the accurately calculated bandgap alignment of ε-Ga ₂ O ₃ , 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 ₂ O ₃ are also investigated. The results show that the saturation currents of ε-Ga ₂ O ₃ HEMTs devices are much larger than that of typical AlGaN HEMTs. For the emerging problem of large leakage current from ε-Ga ₂ O ₃ 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 ₂ O ₃ . Therefore, our results can provide a theoretical basis for the potential applications of ε-Ga ₂ O ₃ in fabricating HEMTs for high-power and high-frequency applications.