Low trap density of oxygen-rich HfO2/GaN interface for GaN MIS-HEMT applications

Abstract

The high-k nature of HfO2 makes it a competitive gate oxide for various GaN-based power devices, but the high trap densities at the HfO2/GaN interface have hindered the application. This work was specifically carried out to explore the interface between GaN and ozone-based atomic-layer-deposited HfO2 gate oxide. Furthermore, the GaN surface is preoxidized before gate oxide deposition to prepare an oxygen-rich HfO2/GaN interface. On the preoxidized GaN surface, a sharper HfO2/GaN interface and amorphous HfO2 bulk form during the subsequent deposition, translating to improved electric performance in metal–insulator–semiconductor (MIS) devices. The ozone-based HfO2 shows a high breakdown electric field (∼7 MV/cm) and a high dielectric constant (∼28). Furthermore, the MIS high electron mobility transistors' negligible VTH hysteresis and parallel conductance measurements reflect the ultralow trap densities of the HfO2/GaN interface (<1012 cm−2 eV−1). Therefore, the proposed HfO2 gate oxide scheme offers a promising solution for developing GaN MIS devices.