Effects of a Spike-Annealed HfO2 Gate Dielectric Layer on the On-Resistance and Interface Quality of AlGaN/GaN High-Electron-Mobility Transistors

Abstract

Various high-k dielectrics have been proposed for AlGaN/GaN MOSHEMTs for gate leakage and drain-current collapse suppression. Hafnium oxide (HfO2) is particularly interesting because of its large bandgap, high dielectric constant, and ferroelectricity under specific phase and doping conditions. However, defects and surface scattering caused by HfO2 dissimilarity and degraded HfO2/GaN interface quality still leave the challenge of reducing the SS and Ron. In this study, we investigated the effects of the first spike-annealed HfO2 (6 nm) layer, compared with the conventional ALD-HfO2 (6 nm) layer in the HfO2 bilayer gate dielectric structure on AlGaN/GaN HEMTs. Both devices exhibit negligible hysteresis and near-ideal (~60 mV/dec) subthreshold slopes of more than three orders of magnitude. The device with the first annealed HfO2 layer exhibited a reduced Ron with notably less gate bias dependency and enhanced output current. On the other hand, the capacitance–voltage and conductance methods revealed that the border and interface trap densities of the device were inferior to those of the conventional HfO2 layer. The trade-off between enhanced electrical performance and oxide traps is discussed based on these results.