Nobuyuki Horikawa

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.

40mΩ / 1700V DioMOS (Diode in SiC MOSFET) for High Power Switching Applications

Device technologies of SiC MOSFETs have nearly matured to the level of mass production and one of the remaining tasks is to serve better solutions in view of both costs and performances for practical systems. Elimination of external reverse diodes in inverter circuits is one of the solutions, by which total area of the SiC chips is greatly reduced leading to lower material cost. A DioMOS (Diode in SiC MOSFET) successfully integrates the reverse diode without any increase of the chip size from the original MOS transistor by utilizing an n-type epitaxial channel under the MOS gate for the reverse conduction path of the diode. The basic concept of the DioMOS has been proposed [1]; meanwhile, further reduction of the on-state resistance together with confirmation of high-speed switching is necessary for its application in power switching systems. In this paper, low on-state resistance (Ron) of 40mΩ and blocking voltage (BVds) of 1700V as well as improved switching performances of DioMOS are demonstrated. The measured results suggest DioMOS to be satisfactory for practical use.

A novel duality-based modeling methodology for reverse current-voltage characteristics of SiC

This paper presents a novel methodology to design a compact but precise SPICE (Simulation Program with Integrated Circuit Emphasis) model which reproduces complete current-voltage (I-V) characteristics of Silicon Carbide (SiC) power devices. The methodology is based on duality relation between one function for the forward I-V characteristics and its inverse function for the reverse I-V characteristics. The simulated and the measured results of static characteristics of DioMOS (Diode integrated SiC MOSFET) have proved that the reverse I-V characteristics are reproduced by the inverse function of the forward I-V characteristics. Moreover, universal applicability of the proposed methodology is proved by other commercially supplied SiC power devices as well.