Epitaxial κ-Ga₂O₃/GaN heterostructure for high electron-mobility transistors

GaN power technology, especially AlGaN/GaN high electron-mobility transistors (HEMTs), has made significant progress in recent years. However, the performance of HEMTs is still limited due to a trade-off between on-resistance and off-state breakdown voltage (BV). Integrating a polar gate dielectric with GaN HEMTs can potentially improve both sheet resistance of the two-dimensional electron gas channel and the field distribution between gate and drain. In this regard, orthorhombic κ-Ga₂O₃ has attractive properties since it is predicted to be strongly polar and highly dielectric while it grows epitaxially on GaN. By successfully integrating crystalline κ-Ga₂O₃ on GaN HEMTs, the channel sheet resistance is reduced by 20% from a reference device with amorphous Al₂O₃ gate dielectric. As a result, the cut-off frequency increases from 4.8 to 9.1 GHz. The dielectric property of κ-Ga₂O₃ also improves BV from 354 to 380 V by reducing the peak electric field in the gate-drain region.