Low Subthreshold Swing Double-Gate β-Ga2O3 Field-Effect Transistors with Polycrystalline Hafnium Oxide Dielectrics

Abstract

We demonstrate low subthreshold swing (SS) double-gate (DG) β-Ga2O3 field-effect transistors (FETs) with polycrystalline hafnium oxide (HfO2) gate dielectrics. The atomic layer deposited HfO2 layer at an elevated temperature of 350 °C without post-deposition annealing has a polycrystalline structure. The threshold voltage is modulated from depletion-to enhancement-mode by independently controlled bottom-gate bias. The SS is reduced to as low as 64 mV/dec with mobility of 20 cm2/Vs while maintaining a high ON/OFF ratio of 107 and negligible hysteresis of 30 mV via double-gate operation. The device shows an ON/OFF ratio of 106 and the SS of 320 mV/dec up to an operating temperature of 250 °C and the OFF-state breakdown voltage of 355 V. The demonstrated DG β-Ga2O3 FETs with the polycrystalline HfO2 layer is a promising structure for energy efficient high temperature device and circuit applications. © 1980-2012 IEEE.