Surface‐oxide‐controlled InAlN/GaN MOS‐HEMTs with water vapor

Abstract

We have investigated the effect of oxidant sources on the performance of InAlN/GaN metal–oxide–semiconductor high electron mobility transistors (MOS‐HEMTs). We clarified that the surface‐oxide of InAlN comprises aluminum oxide (Al2O3) and indium oxide (In2O3) when using conventional oxygen (O2) plasma, and In2O3 causes the gate leakage and current collapse of InAlN/GaN MOS‐HEMTs due to its narrow bandgap and electron traps, such as oxygen vacancies. Then, we proposed water (H2O) vapor oxidation to decrease In2O3 for the surface‐oxide by focusing on the thermal stability of intermediate hydroxide. Aluminum hydroxide [Al(OH)x] is thermally stable because it changes into Al2O3 at 300 °C. On the other hand, indium hydroxide [In(OH)x] is thermally unstable because it desorbs at 150 °C. Therefore, Al2O3 was selectively increased when using 300 °C H2O vapor because of In(OH)x desorption, and the gate leakage and current collapse were successfully reduced due to the decrease in In2O3. We concluded from these results that a key role in improving the performance of InAlN/GaN MOS‐HEMTs is decreasing In2O3 for the surface‐oxide.