Characterization of Buffer-Related Current Collapse by Buffer Potential Simulation in AlGaN/GaN HEMTs

In this paper, the buffer-related current collapse (CC) in AlGaN/GaN HEMTs is investigated by using pulsed I-V measurements and 2-D drift-diffusion simulations. The simulation results indicate that the negative potential (NP), appearing in the Fe-doped buffer under the gate, is found to account for the CC. The NP will induce threshold voltage shifts, in which an inflection point (IP) of the threshold voltage is found. It could be revealed in pulsed I-V characteristics which are significant to depict trapping effect when building a compact large-signal model. The formation mechanism of the IP is detailed. In the end, a simple threshold voltage model is proposed for verification.