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

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
_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
_ON
) and high positive V
_th
. The designed tri-gate device exhibits a high V
_th
of +2.61 V at current density (I
_DS
) = 1 μA/mm, a high maximum current density (IDS, MAX) of 896 mA/mm, a low R
_ON
of 5.0 Ω·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
_ON
,SP) among reported normally off GaN device results with BV > 650 V.