Evaluation of a Gate-First Process for AlGaN/GaN Heterostructure Field-Effect Transistors

Abstract

In this study, we evaluated the annealing temperature and time-dependent electrical properties of AlGaN/GaN heterostructure field-effect transistors (HFETs) utilizing TiN/W/Au as the gate electrode. With the annealing temperature increasing from 750 to 900 °C for the annealing time of 1 min, the sheet resistance of TiN/W/Au films increased gradually while that of the ohmic contact was minimum (0.66 Ω mm) at 800 °C. From the current–voltage characteristics of the Schottky diode and HFETs, it is demonstrated that annealing at 800 °C showed the lowest on-resistance and highest maximum drain current. By prolonging the annealing from 0.5 to 10 min at 800 °C, good device performance was achieved when the annealing time was 1 and 3 min, while the device performance degraded showing an increased gate leakage current and gate resistance with increasing annealing time. These results demonstrated that the TiN/W/Au gate, which can withstand 800 °C annealing for a short time, is suitable for application in the gate-first process for AlGaN/GaN HFETs.