GaN-based high-temperature and radiation-hard electronics for harsh environments

Abstract

We develop novel GaN-based high temperature and radiation-hard electronics to realize data acquisition electronics and transmitters suitable for operations in harsh planetary environments. In this paper, we discuss our research on AlGaN/GaN <i>metal-oxide-semiconductor (MOS) transistors </i>that are targeted for 500 °C operation and &gt;2 Mrad radiation hardness. For the target device performance, we develop Schottky-free AlGaN/GaN MOS transistors, where a gate electrode is processed in a MOS layout using an Al₂O₃ gate dielectric layer. The AlGaN/GaN MOS transistors fabricated with the wide-bandgap gate oxide layer enable Schottky-free gate electrodes, resulting in a much reduced gate leakage current and an improved sub-threshold current than the current AlGaN/GaN field effect transistors. In this study, characterization of our AlGaN/GaN MOS transistors is carried out over the temperature range of 25°C to 500°C. The I_ds- V_gs and I_ds-V_ds curves measured as a function of temperature show an excellent pinch-off behavior up to 450°C. Off-state degradation is not observed up to 400 °C, but it becomes measurable at 450 °C. The off-state current is increased at 500 °C due to the gate leakage current, and the AlGaN/GaN MOS HEMT does not get pinched-off completely. Radiation hardness testing of the AlGaN/GaN MOS transistors is performed using a 50 MeV ⁶⁰Co gamma source to explore effects of TID (total ion dose). Excellent I_ds-V_gs and I_ds-V_ds characteristics are measured even after exposures to a TID of 2Mrad. A slight decrease of saturation current (&#916;I_dss~3 mA/mm) is observed due to the 2Mrad irradiation.