Abstract
A 1.2 kV SiC MOSFET with an integrated heterojunction diode and p-shield region (IHP-MOSFET) was proposed and compared to a conventional SiC MOSFET (C-MOSFET) using numerical TCAD simulation. Due to the heterojunction diode (HJD) located at the mesa region, the reverse recovery time and reverse recovery charge of the IHP-MOSFET decreased by 62.5% and 85.7%, respectively. In addition, a high breakdown voltage (BV) and low maximum oxide electric field (EMOX) could be achieved in the IHP-MOSFET by introducing a p-shield region (PSR) that effectively disperses the electric field in the off-state. The proposed device also exhibited 3.9 times lower gate-to-drain capacitance (CGD) than the C-MOSFET due to the split-gate structure and grounded PSR. As a result, the IHP-MOSFET had electrically excellent static and dynamic characteristics, and the Baliga’s figure of merit (BFOM) and high frequency figure of merit (HFFOM) were increased by 37.1% and 72.3%, respectively. Finally, the switching energy loss was decreased by 59.5% compared to the C-MOSFET.
Highlights
Silicon carbide (SiC) is a wide bandgap (WBG) material that can withstand a higher electric field and has good thermal conductivity compared to silicon (Si), so it is in the spotlight as a next-generation power MOSFET material [1,2,3,4]
Split-gate MOSFETs have critical problems in that the high electric field is concentrated on the split-gate oxide corner and there is a degradation of static characteristics such as on-resistance (RON ) and breakdown voltage (BV)
The IHP-MOSFET showed a 72.3% improvement in the high frequency figure of merit (HFFOM) compared to the C-MOSFET, indicating better dynamic performance
Summary
Silicon carbide (SiC) is a wide bandgap (WBG) material that can withstand a higher electric field and has good thermal conductivity compared to silicon (Si), so it is in the spotlight as a next-generation power MOSFET material [1,2,3,4]. Several structures, including an accumulation-mode split-gate MOSFET and a split-gate MOSFET with floating P+ polysilicon, have been proposed to solve these problems [8,9]. Another way to improve the switching characteristics of 4H-SiC MOSFETs is to improve the reverse recovery characteristics of the body diodes. The SiC MOSFETs have a parasitic PiN body diode composed of a P-base region and an N-drift region, which features high turn-on voltage (VF ) because of the wide energy bandgap. Due to the low turn-on voltage (VF ) of the HJD, the proposed device significantly reduced the reverse recovery charge (QRR ) and reverse recovery time (tRR ) compared to the conventional SiC MOSFET (C-MOSFET). The IHP-MOSFET attained better switching performance in terms of the switching time and switching energy loss
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