SiC transistors could run faster, cooler thanks to research effort

New research coming out of the University of Tokyo hints at silicon-carbide MOSFETs that will be more conductive thanks to a better understanding of their carrier mobility.

In a paper to be delivered at the upcoming 2017 IEEE International Electron Devices Meeting (IEDM), T. Iwamatsu, H. Amishiro, H. Watanabe, K. Kita from the Univeristy of Tokyo and S.Yamakawa, Mitsubishi Electric Corp., will tell how they were able to observe phonon-limited mobility in SiC experimentally for the first time. Up to now, SiC carrier-transport studies have relied on computer models and simulations. These simulations have shown that the dominant mobility-limiting factors are Coulomb scattering at low voltages and surface roughness at higher voltages. But the intrinsic magnitude of the phonon-limiting effect has been unclear. Different values for it have been assumed for modeling studies.

The researchers say they found that the mobility is, at most, one-fourth of presumed values. They also found that surface roughness isn’t the dominant mobility-limiting factor at high voltages.

The finding is important because carrier mobility affects both MOSFET operation speed and conductivity. A semiconductor’s carrier-transport properties determine its mobility, or how fast electrons and holes can move through it. Carrier mobility-limiting factors in SiC include Coulomb scattering, surface-roughness-scattering, and limitations imposed by phonons (vibrations in the material).

Though transistors made from SiC can operate at higher temperatures and/or voltages than silicon devices, a better understanding of SiC’s carrier-transport properties is needed for the fabrication of more efficient, better-performing SiC devices.

The 63rd annual IEEE International Electron Devices Meeting (IEDM) takes place held December 2-6, 2017 at the Hilton San Francisco Union Square hotel. The IEDM is considered the world’s preeminent forum for reporting technological breakthroughs in the areas of semiconductor and electronic device technology, design, manufacturing, physics, and modeling. IEDM is the flagship conference for nanometer-scale CMOS transistor technology, advanced memory, displays, sensors, MEMS devices, novel quantum and nano-scale devices and phenomenology, optoelectronics, devices for power and energy harvesting, high-speed devices, as well as process technology and device modeling and simulation. The event includes a technical program consisting of more than 220 presentations, along with other events.