Improvement of Impact Ionization Effect and Subthreshold Current in InAlAs/InGaAs Metal–Oxide–Semiconductor Metamorphic HEMT With a Liquid-Phase Oxidized InAlAs as Gate Insulator

The oxidation of InAlAs and its application to InAlAs/InGaAs metal-oxide-semiconductor metamorphic high-electron mobility transistors (MOS-MHEMTs) are demonstrated in this study. After the highly selective gate recessing of InGaAs/InAlAs using citric buffer etchant, the gate dielectric is obtained directly by oxidizing the InAlAs layer in a liquid-phase solution at near room temperature. As compared to its counterpart MHEMT, the fabricated InAlAs/InGaAs MOS-MHEMT exhibits a larger tolerance to gate bias, higher breakdown voltage, lower subthreshold current, improved gate leakage current with the effectively suppressed impact ionization effect, and improved radio-frequency performance. Consequently, the liquid-phase oxidation may also be used to produce gate oxides and as an effective passivation on III-V compound semiconductor devices