A Threshold Voltage Model for Charge Trapping Effect of AlGaN/GaN HEMTs

Abstract

In this paper, a threshold voltage model for charge trapping effect of AlGaN/GaN HEMTs is proposed. The quiescent bias stresses are considered for well modeling the current collapse critical points in pulsed I-V curves. Moreover, the low-frequency dispersions due to the charge trapping effect are well disposed by using the proposed model, which are validated by the scattering parameters (S-parameters). Also, a trapping related parameter α is proposed in the model, which can be conveniently used to describe the current collapse critical points offset due to the different acceptor energy levels of the dopants in GaN buffer. Different from our previous threshold voltage model, the proposed model in this paper can accurately model the dynamic threshold voltage shift due to the fast capture and slow emission processes. The verifications are carried out by comparing with the transient measured drain current. The proposed model is also implemented into a large-signal model for further verifications. The improved large-signal model with the threshold voltage shift model is verified by 0.25 μm process AlGaN/GaN HEMTs with pulsed I-V, S-parameters, power sweep and load-pull measurements. More accurate agreements between measured and modeled results have been achieved in terms of output power (Pout), gain and power added efficiency (PAE).