Transport properties of SiO2/AlInN/AlN/GaN metal–oxide–semiconductor high electron mobility transistors on SiC substrate

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Abstract
Unpassivated SiO2/AlInN/AlN/GaN metal–oxide–semiconductor high electron mobility transistors (MOSHEMTs) exhibiting a thin barrier layer are investigated with a particular focus on their dc characteristics dependence on the gate length. The epiwafer exhibits a sheet resistance of ~250 Ω/ and a channel charge density of 7.4 × 1012 cm−2 deduced from the 1 MHz capacitance–voltage curves. The results indicate that the thickness of the AlInN barrier can be reduced below 5 nm without degradation of the insulated gate devices performance. For transistors with gate lengths (LG) between 1.8 and 2.0 µm, dc drain saturation currents densities as high as 1.8 A mm−1 are achieved at +4 V gate–source bias (VGS) with very low reverse gate leakage currents. The electron zero-bias drift mobility was determined to be 1670 cm2 V−1 s−1 from the low-field channel conductance measurements. On the other side, using an analytical model it is found that the maximum output current density at VGS = 0 V can be enhanced by ~23% when LG is scaled from 1.8 µm down to 100 nm. With further improvement of the quality of the gate insulating oxide layer and the implementation of surface passivation, both with the aim of suppressing the observed current collapse, the presented results suggest that these MOSHEMTs could become very attractive for the realization of high-power electronics.

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