Study on the Electrical Characteristics of Al-rich AlGaN HEMT with TiN Gate

In this work, Al 0.85Ga0.15N/Al 0.5Ga0.5N high-electron-mobility transistors (HEMTs) with TiN Schottky gates and source field plates were fabricated and evaluated for high-temperature operation and off-state voltage blocking. The devices maintained gate-controlled operation and an on/off ratio above 10⁴ at 400 °C. Despite a negative threshold voltage shift from −2.9 V at room temperature to −3.7 V at 400 °C, the on-resistance increased by only 10% at the same gate-overdrive voltage, owing to the compensating effects of reduced channel electron mobility and decreased access resistance. The off-state breakdown voltage increased with increasing LGD and the application of a source field plate. A device with LGD = 5 μm and LFP = 2 μm exhibited a breakdown voltage of approximately 1000 V, whereas the maximum breakdown voltage of 1800 V was obtained with LGD = 20 μm and LFP = 2 μm. TCAD simulations showed that the source field plate reduced the electric-field peak at the drain-side gate edge and redistributed the field toward the field plate edge. These results demonstrate stable high-temperature operation and kilovolt-class voltage blocking for high-power applications.