Influence of Nitride Passivation on the Performance of InAlAs/InGaAs HEMTs

AlInAs/InGaAs HEMTs with different gate lengths, ranging from 0.2 to 1.0 ¿m, and on different layer structures were fabricated. The DC- and HF-characteristics were systematically investigated before and after the passivation with PECVD Si3N4. The passivation resulted in an increase in parasitics such as the feedback capacitance (Cgd) and the drain delay time, leading to a slight degradation of the extrinsic fT-values. The intrinsic behaviour of the devices was consistently improved after passivation due to the increase of the transconductance.