Threshold Voltage Engineering of Enhancement-Mode AlGaN/GaN Metal-Oxide-Semiconductor High Electron Mobility Transistors with Different Doping Concentration of in Situ Cl^-Doped Al₂O₃

This work used mist chemical vapor deposition to deposit an in situ Cl- doped Al2O3 film. 0.05 vol%, 0.1 vol%, and 0.15 vol% HCl were added to the precursor solutions for Cl- doping. The recess and Cl- doped Al2O3 gate dielectrics were used to form enhancement-mode AlGaN/GaN metal-oxide-semiconductor high electron mobility transistors. The Cl- doping was confirmed by X-ray photoelectron spectroscopy and the negative charge concentration was extracted by capacitance-voltage method. It was found that the doping concentration affects the gate leakage performance and the carrier transportation mechanisms of the gate leakage were investigated. By using the Cl- doped Al2O3 as the gate dielectric layer, the device performance was improved, including more positive threshold voltage, higher output current at the same overdrive voltage, and over 600 V off-state breakdown voltage. In addition, the temperature-dependent threshold voltage characteristics were investigated to estimate the Cl- dopant runaway.