Masashi Hayashi

Novel SiC power MOSFET with integrated unipolar internal inverse MOS-channel diode

A novel SiC power MOSFET with an integrated unipolar internal inverse diode has been developed for the first time. Our novel SiC MOSFET has two specific features. One is that the growth of the SiC crystal defects caused by the continuous bipolar forward current of the internal diode with pn junction is completely eliminated because the unipolar diode current passes through the MOS channel region. The other is that the very small-size power modules and/or power systems are successfully designed because the external inverse diode chips paired with the transistor chips are not necessary.

Normally-Off 4H-SiC Power MOSFET with Submicron Gate

In order for SiC-MOSFET to be practical in various power electronics applications, low specific on-resistance Ron,sp, high breakdown voltage and “normally-off” characteristics have to be fulfilled even at high temperature. We fabricated a SiC-MOSFET employing a submicron gate with channel length Lg of 0.5μm by a self-aligned implantation and aδ-doped epitaxial channel layer to successfully demonstrate the following features. The normally-off characteristics was confirmed from room temperature to 200°C where the therethold voltages Vth were 2.9V at room temperature and 1.6V at 200°C, respectively. The Ron,sp were 4.6mΩcm2 at room temperature and 9.2mΩcm2 at 200°C, respectively, while the breakdown voltage was greater than 1400V .

Normally-Off 1400V/30A 4H-SiC DACFET and its Application to DC-DC Converter

Large (3.6 x 3.6 mm2) chips of the SiC DACFET were fabricated and mounted in TO220 packages. The drain-source avalanche breakdown voltage without any gate bias (Vgs=0V) is measured to be >1400V. The SiC DACFET keeps the normally-off characteristics even at 150°C. Ron and specific Ron of the SiC DACFET is measured to be 62mΩ and 6.7 mΩcm2 at RT while those at 150°C change to 107 mΩ and 11.6 mΩcm2. The 400V / 3 kW DC-DC switched-mode power-conversion circuit with 100kHz switching was fabricated using the SiC DACFET and the SiC SBD. The turn-off switching loss reduces dramatically using the SiC-DACFET down to 77μJ/pulse which is less than 1/10 of that using the Si-IGBT.