The Influence of Hole Transport in GaN Super-Heterojunction Transistor Switching Time

The superjunction (SJ), historically a silicon technology, has emerged as an effective method to increase blocking voltage with reduced ON-resistance. A previous report of experimentally demonstrated lateral GaN super-heterojunction (SHJ) MOSFETs indicated potential for 10-kV-range low-loss and fast switching. The charging and discharging of p-type regions with holes utilized for creating a charge-balanced drift region may influence device switching time. In this work, a TCAD transient simulation study of an SHJ-FET is presented to understand: 1) the SHJ FET switching behavior and 2) how gate-to-drain spacing, hole mobility, acceptor ionization energy, and hole capture rate by p-type layer ionized acceptors influence switching time. It is revealed that device turn-on is driven by electrostatic potential in the p-GaN. A closed-form analytical model is derived to relate the turn-on time with key device and material parameters. Both TCAD simulation and the analytical model indicate that the turn-on time is in microsecond range for 10-kV-class devices.