Design of a novel SiC MOSFET structure for EV inverter efficiency improvement

Abstract

Inverters for electric vehicle motor drive systems are essential in converting the battery's direct current into alternating current. Si(Silicon) IGBT that is commonly used in inverter modules have large Vce,sat and turn-off time due to p+ drain and tail current. Therefore, inverter modules consist of Si IGBT with relatively low efficiency. If we can use MOSFETs instead of IGBT in inverter modules, it is possible to achieve high efficiency because of short turn-off time and high operating frequency. Yet also has a problem; Si MOSFETs has large on-resistance compared to Si IGBTs. In this study, SiC(Silicon Carbide) was used to make MOSFETs instead of Si. Futhermore, an accumulation channel concept is adapted to a SiC trench MOSFET, namely Trench ACCUFET. Compared with conventional SiC trench MOSFETs, the novel SiC trench ACCUFET structure has not only lower on-resistance but also high breakdown voltage as shown by the simulation results. We fabricated the Trench ACCUFET for verification, and described improvements that is to be made.

A novel 4H‐SiC accumulation mode MOSFET with ultra‐low specific on‐resistance and improved reverse recovery capability

“…Figures 8b and 8c demonstrate the distribution of current density and current flowing lines of the conventional device and the proposed device, respectively. The integrated SBD in the proposed ACCUFET not only avoids the bipolar degradation effect of the device due to only electron current in reverse conduction, but also overcomes the shortcomings of previously reported SiC ACCUFETs [20–23, 33, 34] that have poor even no reverse freewheeling function by themselves in applications. Figure 8d reveals the reverse recovery current curves and the simulation circuit diagram of the two devices.…”

“…In the reverse conduction state of the proposed device ( V SD > 0, V GS < V TH ), the electron barrier of the channel region prevents the electrons flowing from the drain to the source at the channel region. The electrons only flow to the source connected Schottky contacts at the bottom of the trench gates on both sides, which overcomes the drawbacks of poor reverse freewheeling function or no reverse recovery capability at all of the conventional SiC ACCUFETs [20–23, 33, 34].…”

“…However, as for the fundamental ACCUFET, an off‐chip parallel reverse freewheeling diode is required in inductive load applications to conduct the reverse current [24–26]. This is because the fundamental ACCUFETs cannot perform the reverse recovery performance or their own inherent body PN junction diodes have poor reverse recovery performance, which leads to high application loss [20–23, 33, 34].…”

“…This issue hinders the channel resistance from being further reduced [13][14][15][16][17]. On the other hand, the accumulation mode MOSFETs (ACCUFETs) have been proven to achieve low specific on-state resistance (R on,sp ) due to its high electron mobility of the channel accumulation layer [18][19][20][21][22][23]. However, as for the fundamental ACCUFET, an off-chip parallel reverse freewheeling diode is required in inductive load applications to conduct the reverse current [24][25][26].…”

Influence of Parasitic Inductances on Switching Performance of SiC MOSFET

“…There has been a significant effort on the study of SiC MOSFET, but the majority of research have focused on the design, packaging, modeling and application of SiC MOSFET power device [3][4][5][6]. Only a few studies on the influence of parasitic parameters on SiC power MOSFET switching characteristics have been mentioned.…”