Iridium oxides based gate interface of AlGaN/GaN high electron mobility transistors formed by high temperature oxidation

•The impact of 15nm Schottky gate contact layer based on conductive Ir oxides grown by RTA in O2 ambient at 500–800̊C for 1.•Detailed microstructural and interface composition analyses using XRD, SIMS, AES, TEM and AFM revealed presence two crystalline phases – pure Ir and IrO2, the impact of the gradual thermal oxidation of Ir gate layer, the polycrystalline structure of IrO2 gate layer with a small surface roughness and continual sharp gate interface and larger grain sizes Ir gate as the temperature of oxidation increases.•The transformation of Ir gate layer into its crystalline IrO2 phase at oxidation temperatures of 700̊C and 800̊C provides the high barrier gate interface with prevailing thermionic emission transport mechanism.•Accelerated reliability tests confirmed the improved thermal stability especially gate contacts based on high temperature grown IrO2 layers (growth at oxidation temperature of 700 and 800̊C).