Recent Advances in Ga
2
O
3
Power Device Technologies
M. Higashiwaki
1
, M. H. Wong
1
, K. Konishi
1
, K. Sasaki
2,1
, K. Goto
2,3
, R. Togashi
3
,
H. Murakami
3
, Y. Kumagai
3
, B. Monemar
3,4
, A. Kuramata
2
, and S. Yamakoshi
2
1
National Institute of Information and Communications Technology, Koganei, Tokyo 184-8795, Japan
2
Tamura Corporation, Sayama, Saitama 350-1328, Japan
3
Department of Applied Chemistry, Tokyo University of Agriculture and Technology, Koganei, Tokyo 184-
8588, Japan
4
Department of Physics, Chemistry and Biology, Linkӧping University, S-581 83 Linkӧping, Sweden
Phone: +81-42-327-6092, E-mail:
The current mainstream Si power devices are approaching their physical performance
limit. Wide bandgap semiconductors represented by SiC and GaN possess attractive material
properties for power device applications and are thus expected to overcome the limitation of
Si devices. Recently, another wide bandgap semiconductor material - gallium oxide (Ga
2
O
3
) -
has emerged as a new competitor to SiC and GaN in the race toward next-generation power
devices by virtue of the excellent material properties and the relative ease of mass wafer
production. In this talk, following a short introduction of material properties and features of
Ga
2
O
3
, an overview of our recent development progress in device processing and
characterization of Ga
2
O
3
field-effect transistors (FETs) and Schottky barrier diodes (FP-
SBDs) will be reported.
State-of-the-art Ga
2
O
3
metal-oxide-semiconductor FETs (MOSFETs) were fabricated with
unintentionally-doped (UID) β-Ga
2
O
3
(010) epitaxial layers grown on semi-insulating Fe-
doped substrates by ozone molecular beam epitaxy [1]. Selective-area Si-ion (Si
+
)
implantation doping of the UID Ga
2
O
3
epilayer formed the device channel and ohmic
contacts [2], while the high resistivity of UID Ga
2
O
3
was harnessed for planar device
isolation without mesa etching. Room-temperature field-effect electron mobilities in the
Ga
2
O
3
channel were extracted to be 90~100 cm
2
/Vs from long-gate MOSFET structures.
SiO
2
-passivated depletion-mode MOSFETs with a gate-connected field plate (FP)
demonstrated a high off-state breakdown voltage (
V
br
) of 755 V, a large drain current on/off
ratio of over nine orders of magnitude, DC-RF dispersion-free output characteristics, and
stable high temperature operation against thermal stress at 300°C.
We also fabricated and characterized Pt/Ga
2
O
3
FP-SBDs on
n
-
-Ga
2
O
3
drift layers grown on
n
+
-Ga
2
O
3
(001) substrates [3], owing to the success of halide vapor phase epitaxy (HVPE) for
high-speed growth of high-quality Ga
2
O
3
thin films [4, 5]. The illustrative device with a net
donor concentration of 2.4×10
16
cm
-3
exhibited a specific on-resistance of 5.1 mΩ·cm
2
and an
ideality factor of 1.05 at room temperature. Successful FP engineering resulted in a high
V
br
of 1076 V, which was approximately two times larger than those of the SBDs without an FP
[6, 7]. Note that this was the first demonstration of
V
br
of over 1 kV for both Ga
2
O
3
transistors and diodes.
In summary, we succeeded in fabricating depletion-mode Ga
2
O
3
FP-MOSFETs and
vertical Ga
2
O
3
FP-SBDs on single-crystal β-Ga
2
O
3
substrates. Despite the simple structures,
both the FP-MOSFETs and FP-SBDs revealed excellent device characteristics and
demonstrated great potential of Ga
2
O
3
electron devices for power electronics applications.
This work was partially supported by Council for Science, Technology and Innovation
(CSTI), Cross-ministerial Strategic Innovation Promotion Program (SIP), “Next-generation
power electronics” (funding agency: NEDO).
[1] M. H. Wong
et al.
, IEEE Electron Device Lett
37
, 212 (2016), [2] K. Sasaki
et al.
, Appl. Phys. Express
6
, 086502 (2013),
[3] K. Konishi
et al., 74th Device Research Conference IV-A.5, 2016
, [4] K. Nomura
et al.
, J. Cryst. Growth
405
, 19 (2014),
[5] H. Murakami
et al.
, Appl. Phys. Express
8
, 015503 (2015), [6] M. Higashiwaki
et al., Tech. Dig. 73rd Device Research
Conference, pp. 29-30, 2015
, [7] M. Higashiwaki
et al.,
Appl. Phys. Lett.
108
, 133503, (2016).
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