Analysis of the 1st and 3rd Quadrant Transients of Symmetrical and Asymmetrical Double-Trench SiC Power MOSFETs

Juefei Yang,Saeed Jahdi,Phil Mellor,Jose Ortiz-Gonzalez,Bernard Stark,Olayiwola Alatise

doi:10.1109/ojpel.2021.3072503

Juefei Yang, Saeed Jahdi + Show 4 more

Open Access

https://doi.org/10.1109/ojpel.2021.3072503

Copy DOI

Abstract

In this paper, performance at 1 st and 3 rd quadrant operation of Silicon and Silicon Carbide (SiC) symmetrical and asymmetrical double-trench, superjunction and planar power MOSFETs is analysed through a wide range of experimental measurements using compact modeling. The devices are evaluated on a high voltage clamped inductive switching test rig and switched at a range of switching rates at elevated junction temperatures. It is shown, experimentally, that in the 1 st quadrant, CoolSiC (SiC asymmetrical double-trench) MOSFET and SiC symmetrical double-trench MOSFET demonstrate more stable temperature coefficients. Silicon Superjunction MOSFETs exhibits the lowest turn-off switching rates due to the large input capacitance. The evaluated SiC Planar MOSFET also performs sub-optimally at turn-on switching due to its higher input capacitance and shows more temperature sensitivity due to its lower threshold voltage. In the 3 rd quadrant, the relatively larger reverse recovery charge of Silicon Superjunction MOSFET negatively impacts the turn-OFF transients compared with the SiC MOSFETs. It is also seen that among the SiC MOSFETs, the two double-trench MOSFET structures outperform the selected SiC planar MOSFET in terms of reverse recovery.

Highlights

Wide-bandgap devices are considered established devices in power electronics
Silicon Superjunction MOSFETs exhibit more than two times higher voltage and current switching rates at turn-ON compared with the slowest Silicon Carbide (SiC) planar MOSFET, due to large transconductance in spite of the large input capacitance
In the 3rd quadrant operation, its reverse recovery charge results in more switching energy, which increases with temperature

Summary

INTRODUCTION

The wide-bandgap property of SiC enables high breakdown voltage, while its good thermal conductivity allows the devices to operate at higher temperatures. The MOSFET body diode conducts current before turn-off [5], and the stored charge in its drift region leads to current overshoot in the switching transistor during its reverse recovery. The planar structure has a JFET region, yielding an optimum JFET dimension beyond which the on state resistance increases This limits the scaling down of unit cells, and the gate oxide is exposed to high electric field strength which leads to reliability concerns [9]. The P pillars enable a higher voltage ratings with thinner drift regions, enabling lower on-state resistance, but with significant reverse recovery charge in the conduction of Silicon superjunction device. Which is essentially the charging rate of gate-drain capacitance by gate current as follows:

TURN-OFF

Findings

CONCLUSION