Normally-Off HEMT-Based Bipolar p-FET With Enhanced Conduction Capability

A normally-OFF HEMT-based bipolar p-channel field-effect transistor (NH-BiPFET) structure is proposed to enlarge the conduction current density of GaN-based p-channel transistors. In the NH-BiPFET, a normally-OFF p-GaN gate high-electron-mobility transistor (HEMT) is cascaded with a conventional p-channel field-effect transistor (p-FET), leveraging electrons as majority carriers to enhance conduction current substantially. As a result, the drain current density in NH-BiPFET increases to 43.91 mA/mm, approximately 34 times higher than that of a conventional p-FET. Moreover, the NH-BiPFET maintains a high ${I}_{\text {ON}}$ / ${I}_{\text {OFF}}$ ratio and a low gate leakage current comparable to the conventional p-FETs. However, the analysis of switching performance reveals that the slow discharging rate of the floating node between the p-GaN gate and the p-FET drain can lead to a prolonged turn-off transient. To address this issue, an enhanced configuration (ENH-BiPFET) consisting of the NH-BiPFET and an additional HEMT device is further proposed. Even with one more HEMT device, the complementary logic (CL) inverter based on ENH-BiPFET can still save 43.8% area compared to the conventional CL inverters, while maintaining the same operation speed.