Impact of Fin Width on Tri-Gate GaN MOSHEMTs.

In this paper, we present a detailed investigation of the impact of fin width (${w}_{\text {fin}}$) on tri-gate AlGaN/GaN metal–oxide–semiconductor high electron mobility transistors (MOSHEMTs). As ${w}_{\text {fin}}$ is reduced, the threshold voltage (${V}_{\text {TH}}$) increases, which is due to the enhanced gate control (especially for ${w}_{\text {fin}} < {200}$ nm) thanks to the 3-D geometry of the tri-gate, and the reduced carrier concentration (${N}_{\text {s}}$) caused by a more pronounced strain relaxation and sidewall depletion, as explored using Hall and capacitance–voltage (${C}$ – ${V}$) measurements. Normally- OFF operation was achieved for ${w}_{\text {fin}}$ close to the sidewall depletion width (${w}_{\text {dep}}$) of 19.5 nm, since the fin is depleted from its two sidewalls. The impact of ${w}_{\text {fin}}$ on ON-resistance (${R} _{{{ {6{8} {\text {ON}}}}}}$) and current capability (${I} _{\text {D},\text {max}}$) was also investigated, along with the influence of the effective source injection, the trench conduction and the filling factor (FF) on these key characteristics. The degradation caused by the tri-gate fin etching could be fully recovered by increasing the FF. Finally, we show that the tri-gate can reduce gate capacitance (${C}_{\text {G}}$) and charge (${Q}_{\text {G}}$) in normally- ON MOSHEMTs, depending on the design of the tri-gate and the gate voltage (${V}_{\text {G}}$), leading to a smaller ${R}_{{{ {6{8} {\text {ON}}}}}} \cdot {Q}_{\text {G}}$ product that is beneficial for high-frequency switching applications. The results in this paper offer insights into important phenomena in tri-gate GaN devices and are fundamental for the further advance of this technology. [ABSTRACT FROM AUTHOR]