Surface‐Oxide‐Controlled InAlGaN/GaN High‐Electron‐Mobility Transistors Using Al2O3‐Based Insulated‐Gate Structures with H2O Vapor Pretreatment

Herein, Al2O3/InAlGaN/GaN metal–insulator–semiconductor high‐electron‐mobility transistors (MIS‐HEMTs) using H2O vapor pretreatment to decrease the amount of deficient indium oxide (InOx) is successfully developed. InOx acts as an electron trap in the oxide on the surface of the InAlGaN barrier layer. It is clarified that when O2 plasma is used as an oxidant source for atomic‐layer‐deposited (ALD) Al2O3 (O2 plasma‐Al2O3), the forward breakdown voltage increases using the MIS‐HEMT, due to a high density and a low leakage current of O2 plasma‐Al2O3. Furthermore, when using O2 plasma‐Al2O3 for InAlGaN/GaN MIS‐HEMTs, H2O vapor pretreatment is effective in decreasing the amount of InOx and electron traps in the oxide on the surface, thus suppressing current collapse. These results demonstrate the improved output power characteristics of the fabricated Al2O3/InAlGaN/GaN MIS‐HEMT and show the potential of surface‐oxide‐controlled MIS structures as promising process technologies for next‐generation high‐power radio frequency devices.