Near-ideal Ru/N-polar GaN Schottky diode with ultralow reverse leakage

Abstract

N-polar GaN based HEMTs have demonstrated superior performance for solid-state millimeter wave power amplifiers [1] , [2] . To further improve the high-frequency and high-power performance in N-polar GaN HEMTs, using a small gate length while preserving a good aspect ratio is critical. Currently, N-polar HEMTs utilize a thin gate dielectric to reduce gate leakage. This reduces the aspect ratio. Therefore, removing the gate dielectrics, i.e. using Schottky-HEMTs in N-polar GaN is very attractive to pursue highly scaled and high-performance devices. Previous studies [3] – [6] have shown that the barrier heights between the gate metals and N-polar GaN are relatively low and the reverse leakages may be too high to be used in practical Schottky-HEMTs. Here, we report the first investigation of ruthenium (Ru) on N-polar GaN Schottky barrier. The device shows near-ideal Schottky characteristic under reverse bias and forward bias . The barrier height values at various temperatures extracted from the forward bias region and the reverse bias region agree well. The extracted barrier height is 0.77 eV at room temperature. The reverse leakage is ultralow with ~10 -6 A/cm 2 at -5 V and follows ideal thermionic behavior .