GaN Super-Heterojunction FETs With 10-kV Blocking and 3-kV Dynamic Switching

This article reports on two generations of GaN-on-sapphire super-heterojunction (SHJ) transistors, aiming at the realization of 10-kV class power transistors with low static and dynamic ON-resistance. First generation (Gen. 1) GaN SHJ-FETs used a single 2-D electron gas (2DEG) channel design with Schottky gate. Experimental results indicated the feasibility of achieving 10-kV blocking, however, room for improvement to reduce static source-to-drain ON-resistance \textit{R}_{\text{DS},\text{ON}} and dynamic \textit{R}_{\text{DS},\text{ON}} degradation. A second generation (Gen. 2) SHJ-MOSFET was designed using an epitaxy with two 2DEG channels for larger ON-state drain current and smaller \textit{R}_{\text{DS},\text{ON}} . The high-voltage capability and dynamic \textit{R}_{\text{DS},\text{ON}} degradation mitigation were reached by implementing the GaN SHJ design, while simultaneously avoiding surface trapping between the gate and the SHJ structure. Gen. 2 experimentally showed scaling of blocking voltage with SHJ length up to 10 kV, reduced static \textit{R}_{\text{DS,\textit{ON}}} of 71.4 \Omega \cdot mm (73.5 m \Omega \cdot cm ^{\text{2}}\text{)} , low \textit{R}_{\text{DS,ON}}\textit{C}_{\textit{O}} (tr) of \sim 4.9 ps, and controlled current collapse of 123% when switched from an OFF-state bias of 3 kV.