Dr. Yoshiyuki Yonezawa, AIST

As a counter measure towards the global warming and growing demand of electricity for EVs and ICTs, a large introduction and control of renewable energy and storage, and energy savings are inevitable. Under the circumstances, the role of power electronics becomes more significant in the energy value chain. The evolution of power electronics (PE) has been supported by improvements in Si-IGBTs. But since these improvements have reached their physical limit for Si expectations for SiC devices are increasing. SiC has a ten times higher breakdown electrical field compared to that of Si. Thus despite having the same structure, it is expected that such SiC devices offer breakdown voltages (BVs) ten times higher. By replacing 600V to 3.3kV bipolar Si-IGBTs with unipolar SiC-MOSFETs, low conduction and switching loss which enables a higher operating frequency, thus results in a significant reduction in the size of the passive components, as well as the cost of the power electronics equipment.

Similar to the evolution of power devices in silicon, silicon carbide is now under investigation for more advanced high- to ultra-high-voltage power device structures such as SJ-MOSFETs and IGBTs. SiC super junction MOSFET (SJ-MOSFET) structures that can significantly reduce the on-resistance of the drift layer which is expected to break a SiC on resistance unipolar limit. Current SJ-MOSFETs under development range up to 6.5 kV. Furthermore, when the IGBT structure is applied to SiC devices, MOS-controlled switching devices capable of BVs exceeding 10 kV can be fabricated, which is difficult to obtain with Si devices.

In this course recent progress of these SiC SJ-MOSFT and SiC IGBTs are introduced as a next generation of high- to ultra-high voltage power devices for aiming at application of efficient usage of energies in electric distribution system toward low carbon emission society.

Dr. Yonezawa is a chief senior scientist at National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Japan, Advanced Power Electronics Research Center. From 1989 to 2013 he was an engineer at Fuji Electric Co., Ltd. He has made research contributions in solid state laser system development, hard disk media, dielectric thin films for DC/DC converter, and SiC power devices, where he led the SiC group, then joined AIST in 2013. He was a visiting scholar at Stanford University from 1996 to 1998. His current research involves SiC high voltage SJ-MOSFET and ultra-high-voltage IGBTs and related fundamental technologies. He received his Ph.D. degree from Tokyo Institute of Technology in 2011, based on his work in SiC devices and solution growth of SiC crystal.