Normally-Off Tri-Gate GaN MIS-HEMTs with 0.76 m Omega center dot cm(2) Specific On-Resistance for Power Device Applications

Abstract

A GaN metal-insulator-semiconductor high electronmobility 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 mu A/mm, a high maximum current density (I-DS, MAX) of 896 mA/mm, a low R-ON of 5.0 Omega center dot 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,R- SP) among reported normallyoff GaN device results with BV > 650 V.