Development of a diamond transistor with high hole mobility
Unconventional removal of acceptors enhanced performance

Date:
February 24, 2022
Source:
National Institute for Materials Science, Japan
Summary:
Using a new fabrication technique, engineers have developed a
diamond field-effect transistor (FET) with high hole mobility,
which allows reduced conduction loss and higher operational
speed. This new FET also exhibits normally-off behavior (i.e.,
electric current flow through the transistor ceases when no
gate voltage is applied, a feature that makes electronic devices
safer). These results may facilitate the development of low-loss
power conversion and high-speed communications devices.



FULL STORY ========================================================================== Using a new fabrication technique, NIMS has developed a diamond
field-effect transistor (FET) with high hole mobility, which allows
reduced conduction loss and higher operational speed. This new FET also exhibits normally-off behavior (i.e., electric current flow through the transistor ceases when no gate voltage is applied, a feature that makes electronic devices safer). These results may facilitate the development
of low-loss power conversion and high-speed communications devices.


========================================================================== Diamond has excellent wide bandgap semiconductor properties: its bandgap
is larger than those of silicon carbide and gallium nitride, which are
already in practical use. Diamond therefore could potentially be used to
create power electronics and communications devices capable of operating
more energy efficiently at higher speeds, voltages and temperatures. A
number of R&D projects have previously been carried out with the aim
of creating FETs using hydrogen-terminated diamonds (i.e., diamonds
with their superficial carbon atoms covalently bonded with hydrogen
atoms). However, these efforts have failed to fully exploit diamonds'
excellent wide bandgap semiconductor properties: the hole mobility
(a measure of how quickly holes can move) of these diamond-integrated transistors was only 1-10% that of the diamonds before integration.

The NIMS research team succeeded in developing a high-performance FET
by using hexagonal boron nitride (h-BN) as a gate insulator instead
of conventionally used oxides (e.g., alumina), and by employing
a new fabrication technique capable of preventing the surface of hydrogen-terminated diamond from being exposed to air. At high
hole densities, the hole mobility of this FET was five times that
of conventional FETs with oxide gate insulators. FETs with high hole
mobility can operate with lower electrical resistance, thereby reducing conduction loss, and can be used to develop higher speed and smaller
electronic devices. The team also demonstrated normally-off operation of
the FET, an important feature for power electronics applications. The
new fabrication technique enabled removal of electron acceptors from
the surface of the hydrogen-terminated diamond. This was the key to
the team's success in developing the high-performance FET, although
these acceptors had generally been thought to be necessary in inducing electrical conductivity in hydrogen- terminated diamonds.

These results are new mileposts in the development of efficient diamond transistors for high-performance power electronics and communications
devices.

The team hopes to further improve the physical properties of the diamond
FET and to make it more suitable for practical use.

========================================================================== Story Source: Materials provided by National_Institute_for_Materials_Science,_Japan. Note: Content may be
edited for style and length.


========================================================================== Journal Reference:
1. Yosuke Sasama, Taisuke Kageura, Masataka Imura, Kenji Watanabe,
Takashi
Taniguchi, Takashi Uchihashi, Yamaguchi Takahide. High-mobility
p-channel wide-bandgap transistors based on hydrogen-terminated
diamond/hexagonal boron nitride heterostructures. Nature
Electronics, 2021; 5 (1): 37 DOI: 10.1038/s41928-021-00689-4 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2022/02/220224112702.htm

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