Comprehensive Study on the Bias-Dependent Equivalent-Circuit Elements Affected by PECVD SiN Passivation in AlGaN/GaN HEMTs

In this paper, a comprehensive study on the effect of plasma-enhanced chemical-vapor-deposited SiN surface passivation on the bias-dependent small-signal equivalent-circuit elements is carried out for AlGaN/GaN high-electron mobility transistors on a high-resistivity silicon substrate. The direct-current and small-signal performance of the device was found to be improved by surface passivation. The small-signal equivalent-circuit parameters at various gate and drain biases were extracted, and the physical mechanisms of their bias-dependent behaviors before and after passivation are discussed in detail.