High-Performance Normally-OFF AlGaN/GaN Fin-MISHEMT on Silicon with Low Work Function Metal-Source Contact Ledge

We demonstrate a high-performance normally-OFF AlGaN/GaN fin metal-insulator-semiconductor high electron mobility transistor (fin-MISHEMT) on silicon with a low work function metal-source contact ledge (LWFM-SCL). In order to realize the normally-OFF operation, an optimized gate-recessed fin structure is used. The fin structure inherently containing a gate-connected field plate (FP) design improves the breakdown voltage ( ${V}_{\text {BD}}$ ). Moreover, the LWFM-SCL can improve the device overall ON-resistance ( ${R}_{ \mathrm{ON}}$ ) by lowering the gate-source access resistance ( ${R}_{\text {a}}$ ). The proposed device with a gate-drain length ( ${L}_{\text {GD}}$ ) of 7 $\mu \text{m}$ exhibits superior characteristics such as a threshold voltage ( $V_{\text {TH}}$ ) of +1.2 V, maximum drain current ( ${I}_{\text {D, max}}$ ) of 825 mA/mm, ON-state/OFF-state current ( ${I}_{ \mathrm{ON}}/{I}_{ \mathrm{OFF}}$ ) ratio of 109-1010, subthreshold swing (SS) of 76 mV/decade, ${V}_{\text {BD}}$ of 810 V, and specific ${R}_{ \mathrm{ON}}$ ( ${R}_{\text {on, sp}}$ ) of 0.63 $\text{m}\Omega \cdot $ cm2. It also possesses excellent ${V}_{\text {TH}}$ hysteresis, temperature stability, and dynamic ${R}_{ \mathrm{ON}}$ characteristics. These results suggest that the proposed device is very suitable for high power switching applications.