(Invited) Study of HfO2-Based High-k Gate Insulators for GaN Power Device

We discussed about usefulness of HfO2-based high dielectric constant (High-k) materials such as HfO2, HfSiOx and HfAlOx as gate insulator for GaN power device. Here, we systematically studied characteristics of Hf0.55Al0.45Ox gate insulator which fabricated by plasma-enhanced atomic layer deposition and post-deposition annealing (PDA) at 800°C in N2 ambient. The Hf0.55Al0.45Ox film had an amorphous structure but Ga diffusion into Hf0.55Al0.45Ox film was observed after PDA. The k-value of the Hf0.55Al0.45Ox film was 17.2, which was larger than that of HfSiOx (13.5). The Hf0.55Al0.45Ox also showed superior electrical properties such as a minimal flatband voltage (Vfb) hysteresis ( +10 mV) and a relatively small Vfb shift ( £ -0.95 V), as well as a low interface state density (~ 1 ´ 1011 cm-2eV-1 at Ec-E=0.25 eV), and a high breakdown electric field (8.6 MVcm-1). Based on these experimental data and previous our research of HfO2 and HfSiOx films, we concluded the HfSiOx and HfAlOx had candidate materials as gate insulator for GaN power device.