Multi-channel tri-gate normally-on/off AlGaN/GaN MOSHEMTs on Si substrate with high breakdown voltage and low ON-resistance

Abstract

In this work, we present multi-channel tri-gate AlGaN/GaN metal-oxide-semiconductor high-electron-mobility transistors (MOSHEMTs) for high-voltage applications. A heterostructure with multiple AlGaN/GaN layers was used to form five parallel two-dimensional-electron-gas (2DEG) channels to reduce the ON-resistance (RON), simultaneously modulated by the 3-dimensional tri-gate electrodes. The tri-gate is a unique technology to control the multi-channels, providing enhanced electrostatics and device performance, and, in turn, the multi-channels are exceptionally suited to address the degradation in drain current (ID,max) caused by the tri-gate. With a tri-gate width (w) of 100 nm, normally-on multi-channel tri-gate transistors presented 3×-higher maximum drain current (ID,max), 47%-smaller RON, as well as 79%-higher maximum transconductance (gm,max), as compared to counterpart single-channel devices. Using the channel depletion through the tri-gate sidewalls, normally-off operation was also achieved by reducing w below the sidewall depletion width (wdep), resulting in a positive threshold voltage (VTH) of 0.82 V at 1 μA/mm. The devices presented a high breakdown voltage (VBR) of 715 V, which reveals a promising future platform for high-voltage low-RON GaN transistors.