The impact of defect evolution on the electrical performance of AlGaN/GaN HEMT after 14-MeV neutron irradiation

Abstract

In this work, we study the electrical performance of AlGaN/GaN high-electron-mobility transistors following irradiation with 14 MeV neutrons at fluences of 3 × 1012, 7.4 × 1012, 1.2 × 1013, and 1.0 × 1014 n/cm2. The results reveal that at a neutron fluence of 7.4 × 1012 n/cm2, there is a notable increase in the saturation drain current, a negative shift in threshold voltage, and an enhancement in peak transconductance. As the fluence continues to increase, the electrical characteristics of the device begin to deteriorate. However, at a fluence of 1.0 × 1014 n/cm2, the electrical performance is still better than that before irradiation. The defect evolution induced by neutron irradiation is studied by utilizing low-frequency noise (LFN) and deep-level transient spectroscopy (DLTS) techniques. LFN analysis shows only slight changes in interface state density, while DLTS results reveal a significant reduction in deep-level defects after irradiation. We speculate that bulk defects in the GaN or AlGaN layers predominantly influence device performance variations. Neutron irradiation facilitates the recombination of original defects, thereby decreasing the concentration of deep-level defects in the device. This decrease in deep-level defects alleviates carrier trapping by defects, resulting in an increased carrier concentration and improved electrical performance of the device.