Low Switching Loss Split-Gate 4H-SiC MOSFET With Integrated Heterojunction Diode

Abstract

A 4H-SiC MOSFET with p-type region injection and integrated split gate and heterojunction diode is proposed in this paper. Compared with the conventional MOSFET, the proposed structure has a lower on-resistance and switching loss. And the gate oxide layer has been well protected by the p-type region, which reduces the electric field in gate oxide layer at the off-state. The on-resistance of device can be greatly reduced by increasing the doping concentration of current spreading layer and will not cause a huge electric field in gate oxide layer. The specific on-resistance is decreased by about 27.8% and the static characteristic (BV2/ $\text{R}_{\mathrm{ on,sp}}$ ) of the device is improved about 37.3%. SiC material has a high third quadrant turn-on voltage due to its wide band gap characteristics. The use of heterojunction integration can take place of parasitic body diode and reduce its turn-on voltage, avoid the bipolar degradation effect, and improves the reverse recovery characteristics. To evaluate the dynamic performance, the reverse transmission capacitance ( $\text{C}_{\mathrm{ rss}}$ ) and gate-drain charge ( $\text{Q}_{\mathrm{ gd}}$ ) of the proposed structure have been studied in this paper via numerical simulations. Based on the simulation, the HF-FOM ( $\text{C}_{\mathrm{ rss}} {\times }\text{R}_{\mathrm{ on,sp}}$ ) and HF-FOM2 ( $\text{Q}_{\mathrm{ gd}} {\times }\text{R}_{\mathrm{ on,sp}}$ ) of the proposed structure are decreased by about 87% and 86%, respectively. Meanwhile, the reverse turn-on voltage and reverse recovery characteristics are also improved, and the total energy loss decreases by about 37.3%.

Keywords

• Silicon carbide
• specific on-resistance
• switching energy loss
• figure of merit
• heterojunction diode