Bias Dependence of Radiation Response and Reliability of AlGaN/GaN HEMTs
During the last three decades, GaN-based HEMTs are increasingly developed for their excellent application for high power, high frequency and radiation-tolerance. The improvements in GaN-based HEMTs fabrication result in a material with better quality and devices with better performance, which makes the defects generated during use a more obvious factor in device reliability. This results in a different degradation behavior after stress and some phenomena not observed before such as total ionizing dose effects. In this work, we tested AlGaN/GaN HEMTs with several different structures and growing processes. The bias dependence of reliability and radiation response of AlGaN/GaN HEMTs are studied. Density functional theory (DFT) calculations and low frequency 1/f noise measurements are used to help identify the possible defects responsible for the electrical stress induced degradation and radiation effects. We first compare the hot carrier degradation and annealing performance and total ionizing dose effects in devices with or without a passivation layer. Hydrogenated ON defects are found to be important in hot carrier effects and total ionizing dose effects in AlGaN/GaN HEMTs. Then the bias dependence of high field stress and its combination effects with X-ray and proton irradiation are evaluated. Different worst bias case was found in devices with different growing processes. This is attributed to multiple defects that occur in different locations in the devices. These results emphasize the need to test devices under a wide range of conditions during characterization and qualification testing.