Proton Irradiation Effects on Scandium Oxide/Gallium Nitride MOS Diodes
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Proton Irradiation Effects on Scandium Oxide/Gallium Nitride MOS Diodes K. Allums1, B. Luo2, R. Mehandru2, B. P. Gila1, R. Dwivedi3, T.N. Fogarty3, R. Wilkins3, C. R. Abernathy1, F. Ren2, S. J. Pearton1 1
Department of Materials Science and Eng., University of Florida, Gainesville, FL 32611 Department of Chemical Engineering, University of Florida, Gainesville, FL 32611 3 Center of Applied Radiation Research, Prairie View A&M University , Prairie View, TX 77446 2
ABSTRACT The stability to proton radiation of GaN metal oxide semiconductor (MOS) diodes fabricated using the novel gate dielectric Sc2O3 was investigated. The MOS diodes were fabricated by depositing the dielectric with molecular beam epitaxy onto MOCVD-grown GaN on sapphire. The stability of GaN Schottky diodes was also investigated for comparison. Current-voltage (I-V) and capacitance-voltage (C-V), were employed to monitor any change in the electrical characteristics of the diodes. Preliminary testing indicates that the GaN-based diodes are in fact affected by proton irradiation, but only at fairly high doses. Doses equivalent to 10 years in low earth orbit, ~5x109 cm-2, produce a decrease in the reverse breakdown field in both Schottky and MOS diodes. However, even after irradiation, the GaN MOS diodes showed twice the reverse breakdown voltage of non-irradiated Schottky diodes. Further, while the Schottky diodes showed reduced forward breakdown voltage, the MOS diodes showed no change in forward breakdown. These results suggest that the oxide/GaN interface is stable and is not being damaged by the radiation. The change in reverse breakdown is most likely due to generation of damage in the GaN resulting in the formation of shallow donors. INTRODUCTION AlGaN/GaN high electron mobility transistors (HEMTs) have demonstrated remarkable advances in microwave and low noise operation [1-6]. Potential applications for such devices include broad-band satellite transmission for communications and forecasting systems. In this environment, radiation-resistance of the devices is of utmost importance.. Previous research has shown that InGaN/GaN light-emitting devices suffered little change in their electrical characteristics for 2MeV proton irradiation at a dose of 1.7×1012 cm-2 [7], although the optical output intensity was significantly degraded. In general, GaN is 2-3 orders of magnitude more resistant than GaAs to decreases in its luminescence due to proton irradiation [8,9]. Decreases of ~70% in transconductance and saturation current of AlGaN/GaN HEMTs were observed for 1.8 MeV proton doses of 1014cm-2 [10]. Additional research in the field of radiation damage on AlGaN/GaN HEMTs has shown that 80% of the initial device performance can be recovered via annealing after irradiation with a 5x 109 cm-2 dose of 40 MeV proton [11]. In this study we report on the effects of 40 MeV proton irradiation and the effect of varying the fluence from 5x 109 cm-2 to 5x 1010 cm-2 on the stability of metal oxide semiconductor (MOS) diodes employing scandium oxide as the gate di
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