Investigation of the degradations in power GaN-on-Si MIS-HEMTs subjected to cumulative γ-ray irradiation

In this work, GaN-on-Si power Metal-Insulator-Semiconductor High Electron Mobility Transistors (MIS-HEMTs) are irradiated through different regimes of cumulative γ-ray irradiation, namely 1, 2, 3, 4, and 5 kGy for the first sample; 1, 3, and 5 kGy for the second sample; 1, 5, and 10 kGy for the third sample; and 1, 10, and 20 kGy for the fourth sample. After each irradiation dose, drain current (ID), threshold voltage (VTh), and gate leakage current (Ig) are electrically characterized in all the samples. An improvement in ID with a shift in VTh is observed in all the samples, which saturates after a higher irradiation dose. X-ray photoelectron spectroscopy (XPS) analysis confirms creation of nitrogen vacancies that act as donor and improves the ID. No significant change in Ig is observed except for an increase in noise in gate leakage current. Scanning electron microscopy (SEM) shows the Al-based metallization pad degrades due to formation of small cavities. Finally, energy dispersive X-ray (EDX) analysis confirms the formation of Al native oxides due to γ-ray irradiation.