Among various polymorphic phases of gallium oxide (Ga₂O₃), α-phase Ga₂O₃ has clear advantages such as its heteroepitaxial growth as well as wide bandgap, which is promising for use in power devices. In this work, we demonstrate α-Ga₂O₃ MOSFETs with hybrid Schottky drain (HSD) contact, comprising both Ohmic and Schottky electrode regions. In comparison with conventional Ohmic drain (OD) contact, a lower on-resistance (R_on) of 2.1 kΩ mm is achieved for variable channel lengths. Physics-based TCAD simulation is performed to validate the turn-on characteristics of the Schottky electrode region and the improved R_on. Electric-field analysis in the off-state is conducted for both the OD and HSD devices. Furthermore, a record breakdown voltage (BV) of 2.8 kV is achieved, which is superior to the 1.7 kV of the compared OD device. Our results show that the proposed HSD contact with a further optimized design can be a promising drain electrode scheme for α-Ga₂O₃ power MOSFETs.

The ferroelectric switching behavior of a metal–ferroelectric AlScN–HfO₂ interlayer–metal (MFIM) capacitor was investigated at variable temperatures and compared with an MFM capacitor. Although the MFIM capacitor demonstrated an inferior remnant polarization (2P_r value of 74 µC/cm²), it exhibited a reduced leakage current (×1/100) and higher breakdown field. The MFIM showed a stable change in 2P_r from room temperature to 200 °C and an enhanced endurance of ~10⁴ cycles at 200 °C; moreover, the leakage current was less degraded after the cycling tests. Thus, the ferroelectric AlScN with a thin HfO₂ interlayer can enhance the reliability of ferroelectric switching.

In this Letter, we demonstrate heteroepitaxial α-Ga2O3 MOSFETs using an aluminum scandium nitride (AlScN) ferroelectric gate stack. Owing to ferroelectric effects, α-Ga2O3 MOSFETs with the AlScN/HfO2 gate stack (FGFET) exhibited enhanced electrical performance compared with a HfO2 gate dielectric (IGFET) for variable gate–drain lengths (10, 15, 20 μm). A remnant polarization value of the AlScN deposited on a HfO2 layer was measured to be about 30 μC/cm2. The subthreshold swing (SS) and field-effect mobility (μFE) of IGFET was extracted at 1814 mV/dec and 13.9 cm2/V s, respectively. However, the FGFET exhibits a reduced SS of 552 mV/dec with enhanced μFE of 42.7 cm2/V s owing to the negative capacitance of the ferroelectric AlScN. Furthermore, a lateral figure-of-merit of 17.8 MW/cm2 was achieved for the FGFET, far surpassing the 8.3 MW/cm2 of the IGFET. The proposed ferroelectric AlScN/HfO2 stack can be a promising gate structure for improving both transfer and breakdown characteristics in heteroepitaxial α-Ga2O3 power devices.

In this study, we demonstrate a $\beta $ -Ga2O3 ferroelectric field-effect transistor (Fe-FET) using a sputtered aluminum scandium nitride (AlScN) gate dielectric. The device exhibits a steep subthreshold swing as low as 56 mV/dec with a high on/off ratio of $\sim 10^{\mathbf {{8}}}$ and on-resistances of 201 and $185~\Omega \cdot $ mm for the polarization states. Furthermore, wide threshold voltage modulation from -23.4 to 3.5 V is achieved via gate pulses. Finally, retention and endurance tests show stable depletion (D-) and enhancement (E-) mode switching for up to 10,000 cycles. These results suggest the potential of the proposed $\beta $ -Ga2O3 Fe-FET with AlScN gate structure for monolithic integration of $\beta $ -Ga2O3 NMOS logic circuits.

In this study, the influence of HfO₂ interlayer thickness on the performance of heteroepitaxial α-Ga₂O₃ layer-based metal–insulator–semiconductor–insulator–metal (MISIM) ultraviolet photodetectors is examined. A thin HfO₂ interlayer enhances the interface quality and reduces the density of interface traps, thereby improving the performance of UVC photodetectors. The fabricated device with a 1 nm HfO₂ interlayer exhibited a significantly reduced dark current and higher photocurrent than a conventional metal–semiconductor–metal (MSM). Specifically, the 1 nm HfO₂ MISIM device demonstrated a photocurrent of 2.3 μA and a dark current of 6.61 pA at 20 V, whereas the MSM device exhibited a photocurrent of 1.1 μA and a dark current of 73.3 pA. Furthermore, the photodetector performance was comprehensively evaluated in terms of responsivity, response speed, and high-temperature operation. These results suggest that the proposed ultra-thin HfO₂ interlayer is an effective strategy for enhancing the performance of α-Ga₂O₃-based UVC photodetectors by simultaneously suppressing dark currents and increasing photocurrents and ultimately demonstrate its potential for stable operation under extreme environmental conditions.

We present monolithic integrated, $\alpha $ -Ga2O3 reconfigurable NAND and NOR logic gates. Fabricated $\alpha $ -Ga2O3 field-effect transistors with a ferroelectric AlScN gate stack (FeFET) exhibit memory window of up to 5.5 V at ${V}_{\text {DS}} = 1$ V. Threshold voltage modulation of ~3.8 V is achieved via a program (10 V, 1 s) and erase pulse (−20 V, 1 s), respectively. Moreover, voltage transfer curves of the logic circuit as an inverter confirm hysteretic behaviors with a higher gain during a reverse sweep. Finally, reconfigurable logic operations are successfully demonstrated via two distinct input pulses and a source bias to the driver FeFET. The results demonstrate viability of monolithic integrated, compact Ga2O3 logic circuits.