High on/off current ratio AlGaN/GaN MOS-HEMTs employing RF-sputtered HfO2 gate insulators

We fabricated AlGaN/GaN metal–oxide–semiconductor high-electron-mobility transistors (MOS-HEMTs) on Si substrates with RF-sputtered HfO2 as a gate insulator. We obtained a high breakdown voltage of 1524 V and a high on/off current ratio of 2.37 × 1010 in the MOS-HEMT with a 15 nm-thick RF-sputtered HfO2 while a conventional HEMT had 470 V and 7.61 × 103. The MOS-HEMT with the HfO2 showed a gate leakage current of −67 pA mm−1 at VGS = −10 V and VDS = 100 V and the drain leakage current was not considerably altered for 100 s. However, the conventional HEMT without a gate insulator had a large gate leakage current of −44.7 µA mm−1 and the drain leakage current was increased from 57.5 to 496 µA mm−1 for 100 s. We have also evaluated the blocking characteristics and passivation effects of HfO2 by measuring various electrical properties such as pulsed I–V and the surface leakage current at a mesa-isolated two-ohmic pad before and after HfO2 sputtering.