Country for PR: Japan
Contributor: Kyodo News JBN
Friday, July 29 2022 - 15:00
New Diamond Transistor Exhibits High Hole Mobility: WPI-MANA
TSUKUBA, Japan, July 29, 2022 /Kyodo JBN-Asianet/ --

A research team at the International Center for Materials Nanoarchitectonics 
(WPI-MANA), using a new fabrication technique, has developed a diamond 
field-effect transistor with high hole mobility, which can lead to reduced 
conduction loss and higher operational speeds.


Field-effect transistors (FETs) are semiconductor devices that can switch 
electric power and amplify electric signals. FETs made of wide-bandgap 
semiconductors can handle high power efficiently and are useful for power 
electronics and communications. The use of SiC and GaN is therefore growing, 
but diamond has a wider bandgap and more desirable properties that could boost 
device performance.

The team used a new fabrication technique to develop the FET, wherein it 
fabricated the transistor with hexagonal boron nitride as a gate insulator and 
without exposing the diamond's surface to air. The advantage is that it can 
reduce the density of negative charges on the diamond surface. If there are 
negative charges, they produce random Coulomb potential, which scatters the 
holes when they conduct near the diamond surface. This degrades the 
effectiveness of hole conduction and decreases the mobility of the holes.

Also, with the negative charges, even if no gate voltage is applied, there are 
holes, and so the transistor is "normally on," and this is not suitable for 
power electronics applications.

"In contrast, in our new technique, we can reduce the density of negative 
charges on the diamond surface. So the holes are less scattered, and therefore 
we can obtain higher mobility," said team leader Dr. Takahide Yamaguchi. "This 
also results in 'normally-off' operation, which is desirable for power 

Dr. Yamaguchi pointed to some possible applications of this breakthrough. "Our 
new approach for fabricating diamond transistors could be used to make low-loss 
switches for power electronics and high-frequency high-output amplifiers for 

Research Highlights Vol. 78

MANA Research Highlights

Source: International Center for Materials Nanoarchitectonics (WPI-MANA), 
National Institute for Materials Science (NIMS)