Impact of CF4 plasma treatment on threshold voltage and mobility in Al2O3/InAlN/GaN MOSHEMTs

Abstract

The shift of the threshold voltage Vth in Al2O3/InAlN/GaN metal–oxide–semiconductor high-electron-mobility transistors (MOSHEMTs) is demonstrated by CF4 plasma treatments. The accompanying channel mobility degradation is monitored to understand the tradeoff design space. The effective negative charge introduced by the F plasma treatments at the oxide interface is found to be as high as −0.73 × 1013 cm−2 (mobility > 500 cm2 V−1 s−1), sufficient to fully compensate for the net polarization charge in Al0.15GaN/GaN HEMTs. Although it is difficult to obtain Vth ≫ 0 V owing to the high polarization charges in InAlN, these MOSHEMTs with 1 µm gates show very low leakage (∼1 × 10−11 A/mm), low hysteresis, and low dispersion.