Normally-Off Tri-Gate GaN MIS-HEMTs with 0.76 mΩ·cm2 Specific On-Resistance for Power Device Applications

Abstract

A GaN metal–insulator–semiconductor high electron mobility transistor (MIS-HEMT) using tri-gate architecture and hybrid ferroelectric charge trap gate stack is demonstrated for normally-off operation. Compared with the conventional planar device, the tri-gate device has the 2-D electron gas (2-DEG) channel exposed on the nanowire sidewalls, so that the trapped charges in the HfON charge-trapping layer can easily deplete the channel from the sidewalls, leading to a high positive threshold voltage ( ${V}_{\text {th}}$ ) to realize the normally-off operation. Moreover, through this electrostatic control on the sidewall, a high density of negative charge caused by hybrid ferroelectric charge trap gate stack with the optimized tri-gate structure, the tri-gate device can achieve normally-off GaN device with both low on-resistance ( ${R}_{ \mathrm{ON}}$ ) and high positive ${V}_{\text {th}}$ . The designed tri-gate device exhibits a high ${V}_{\text {th}}$ of +2.61 V at current density ( ${I}_{\text {DS}}) = 1\,\,\mu \text{A}$ /mm, a high maximum current density ( ${I}_{\text {DS, MAX}}$ ) of 896 mA/mm, a low ${R}_{ \mathrm{ON}}$ of $5.0~\Omega \!\!\cdot \!\!\text {mm}$ and a high breakdown voltage (BV) of 788 V. To the best of our knowledge, the proposed tri-gate device shows the lowest specific on-resistance ( ${R}_{ \mathrm{ON}, \text {SP}}$ ) among reported normally-off GaN device results with BV >650 V.