Press Release
Keywords：power devices, gallium oxide, novel material, electric vehicle, Kyoto University, startup

2018 July 13

Ground breaking work on Gallium Oxide（Ga2O3）normally-off transistor～Paved a way for Gallium Oxide as standard material for power semiconductor～

FLOSFIA Inc.
Kyoto University【Background】
Minimizing conversion loss of power devices

is criticalin order to realize energy-saving society. The power devices
are the key components for transferring electricity between
its AC and DC forms and changing its voltage andfrequency and integrated in AC adapter, electric vehicles,
robots and home appliances. For power devices, silicon
dominates, generating sales of more than $20 billion perannum. However, the silicon power devices are far fromperfect. When deployed in power systems, 10 percent ofelectrical energy can be wasted as heat − and addressing
this weakness is not easy, because silicon devices areapproaching their theoretical limit. Industry has beenchallenging to achieve higher efficiencies with new
semiconductor materials.
Gallium Oxide (Ga2O3) is a very promising material for

Figure 1 I-V curve of normally-off Ga2O3 MOSFET

the next generation power devices. It comes in five different
phases with its α-phase which takes the corundum crystal structure possessing the most attractive materialproperties. Kyoto University demonstrated the world-first single crystal growth of corundum α-Ga2O3 onsapphire in 2008. In 2015, FLOSFIA fabricated α-Ga2O3 schotty barrier diode (SBD) showing specific onresistance of 0.1mΩcm2, the world’s lowest specific on-resistance ever. FLOSFIA, then, launched anengineering sample of α-Ga2O3 SBD packaged in TO220, a big step toward commercialization.
Another challenge FLOSFIA has been taking is to demonstrate corundum α-Ga2O3 metal-oxidesemiconductor field-effect transistor (MOSFET). In 2016, FLOSFIA and Kyoto University jointly discovered ptype Iridium oxide (Ir2O3), which has the same corundum structure as the α-Ga2O3, could be expected to form
a gallium oxide-based power MOSFET.
【Results】
FLOSFIA successfully demonstrated α-Ga2O3 normally off MOSFET. (Figure 1) The world-first α-Ga2O3
normally-off MOSFET comprises of N+ source/drain layer, p-type well layer, gate insulator, and electrodes.
(Figure 2 and 3) The gate threshold voltage extrapolated from I-V curve was 7.9V. The device is made of anovel p-type corundum semiconductor which functions as an inversion layer. This is a ground-breaking work
since there has been no theoretical study predicting p-type material which is compatible with n-type Ga2O3 until
we discovered p-type Ir2O3 in 2016, and thus it has been considered challenging to realize normally-off
MOSFET.

1Press Release

Inversion Channel

単位：μmGate Electrode(positive bias)
Source Electrode

Drain ElectrodeN+ source layer

N+ drain layer
P well layer

Sapphire Substrate

Figure 2 Cross sectional device schematic

Figure 3 Optical micrograph of normally-off Ga2O3 MOSFET【Road to commercialization】
FLOSFIA plans to manufacture corundum α-Ga2O3 power devices, GaOTM series, starting from SBD in
TO220 and then MOSFET, which will be integrated in AC adopters, driver circuit of robots, electric vehicles,
home appliances, power conditioner for solar cells, and so on. The GaOTM has a potential to miniaturizeinverters down to tenths of and driving cost down to half of conventional ones while maximizing conversion
efficiency.
【FLOSFIA Inc】
FLOSFIA Inc., headquartered in Kyoto, Kyoto prefecture, Japan, is a spin-off from a research of Kyoto
University, specializing in film-formation by mist chemical vapor deposition (CVD). Making use of physicalproperties of gallium oxide (Ga2O3), FLOSFIA has devoted to development of low-loss power devices.
FLOSFIA succeeded in a development of a Schottky Barrier Diode (SBD) with the lowest specific on-resistanceof any SBDs currently available on the market (through an internal investigation), realizing technologies linked
to power loss reduction that is reduced up to 90 percent less than before. FLOSFIA produces a variety of thinfilms, enhancing MISTDRY™ technology, achieving commercialization of power devices, and realizing
application of its technology to electrode materials, oxide compounds with functional properties for electronic
devices, plating and polymers.
Company name: FLOSFIA Inc.
Address: Kyodai Katsura Venture Plaza North Bldg., 1-36, Goryo ohara, Nishikyo-ku, Kyoto 615-8245, Japan
President CEO: Toshimi Hitora
Capital: 2,260 million yen (including capital reserve)
HP : http://flosfia.com【For inquiries regarding this matter】
FLOSFIA Inc.
Takuto Igawa [Vice President of sales]
TEL：81-75-963-5202 FAX：81-75-320-1712

Mail：sales@flosfia.com

Kyoto University Advanced Electronic Materials Laboratory
Shizuo Fujita [Professor]
TEL：81-75-383-3030 FAX：81-75-383-3050 Mail：fujitasz@kuee.kyoto-u.ac.jp
Kyoto University Advanced Electronic Materials Laboratory
Kentaro Kaneko [Assistant Professor]
TEL：81-75-383-3039 FAX：81-75-383-3050 Mail：ken-kaneko@kuee.kyoto-u.ac.jp2