By systematically changing growth parameters, the growth of β-(AlxGa1−x)2O3/Ga2O3 (010) heterostructures by plasma-assisted molecular beam epitaxy was optimized. Through variation of the Al flux under O-rich conditions at 600 °C, β-(AlxGa1−x)2O3 (010) layers spanning ∼10% to ∼18% Al2O3 were grown directly on β-Ga2O3 (010) substrates. Nominal β-(AlxGa1−x)2O3 (010) compositions were determined through Al:Ga flux ratios. With x = ∼0.18, the β-(AlxGa1−x)2O3 (020) layer peak in a high-resolution x-ray diffraction (HRXRD) ω-2θ scan was barely discernible, and Pendellösung fringes were not visible. This indicated that the phase stability limit of Al2O3 in β-Ga2O3 (010) at 600 °C was less than ∼18%. The substrate temperature was then varied for a series of β-(Al∼0.15Ga∼0.85)2O3 (010) layers, and the smoothest layer was grown at 650 °C. The phase stability limit of Al2O3 in β-Ga2O3 (010) appeared to increase with growth temperature, as the β-(AlxGa1−x)2O3 (020) layer peak with x = ∼0.18 was easily distinguishable by HRXRD in a sample grown at 650 °C. Cross-sectional transmission electron microscopy (TEM) indicated that β-(Al∼0.15Ga∼0.85)2O3 (010) layers (14.4% Al2O3 by energy dispersive x-ray spectroscopy) grown at 650 °C were homogeneous. β-(Al∼0.20Ga∼0.80)2O3 (010) layers, however, displayed a phase transition. TEM images of a β-(Al∼0.15Ga∼0.85)2O3/Ga2O3 (010) superlattice grown at 650 °C showed abrupt layer interfaces and high alloy homogeneity.

1.
B. J.
Baliga
,
Semicond. Sci. Technol.
28
,
074011
(
2013
).
2.
N.
Suzuki
,
S.
Ohira
,
M.
Tanaka
,
T.
Sugawara
,
K.
Nakajima
, and
T.
Shishido
,
Phys. Status Solidi
4
,
2310
(
2007
).
3.
H.
Peelaers
and
C. G.
Van de Walle
,
Phys. Status Solidi B
252
,
828
(
2015
).
4.
M.
Higashiwaki
,
K.
Sasaki
,
A.
Kuramata
,
T.
Masui
, and
S.
Yamakoshi
,
Appl. Phys. Lett.
100
,
013504
(
2012
).
5.
B. J.
Baliga
,
J. Appl. Phys.
53
,
1759
(
1982
).
6.
K.
Sasaki
,
M.
Higashiwaki
,
A.
Kuramata
,
T.
Masui
, and
S.
Yamakoshi
,
IEEE Electron Device Lett.
34
,
493
(
2013
).
7.
M.
Higashiwaki
,
K.
Sasaki
,
T.
Kamimura
,
M. H.
Wong
,
D.
Krishnamurthy
,
A.
Kuramata
,
T.
Masui
, and
S.
Yamakoshi
,
Appl. Phys. Lett.
103
,
123511
(
2013
).
8.
K.
Shimamura
,
E. G.
Víllora
,
K.
Domen
,
K.
Yui
,
K.
Aoki
, and
N.
Ichinose
,
Jpn. J. Appl. Phys.
44
,
L7
(
2005
).
9.
J. B.
Varley
and
A.
Schleife
,
Semicond. Sci. Technol.
30
,
024010
(
2015
).
10.
N.
Ueda
,
H.
Hosono
,
R.
Waseda
, and
H.
Kawazoe
,
Appl. Phys. Lett.
70
,
3561
(
1997
).
11.
E. G.
Villora
,
K.
Shimamura
,
Y.
Yoshikawa
,
T.
Ujiie
, and
K.
Aoki
,
Appl. Phys. Lett.
92
,
202120
(
2008
).
12.
Y.
Tomm
,
P.
Reiche
,
D.
Klimm
, and
T.
Fukuda
,
J. Cryst. Growth
220
,
510
(
2000
).
13.
Z.
Galazka
 et al,
Cryst. Res. Technol.
45
,
1229
(
2010
).
14.
H.
Aida
,
K.
Nishiguchi
,
H.
Takeda
,
N.
Aota
,
K.
Sunakawa
, and
Y.
Yaguchi
,
Jpn. J. Appl. Phys.
47
,
8506
(
2008
).
15.
K.
Sasaki
,
A.
Kuramata
,
T.
Masui
,
E. G.
Víllora
,
K.
Shimamura
, and
S.
Yamakoshi
,
Appl. Phys. Express
5
,
035502
(
2012
).
16.
M. H.
Wong
,
K.
Sasaki
,
A.
Kuramata
,
S.
Yamakoshi
, and
M.
Higashiwaki
,
Appl. Phys. Lett.
106
,
032105
(
2015
).
17.
S. W.
Kaun
,
M. H.
Wong
,
U. K.
Mishra
, and
J. S.
Speck
,
Semicond. Sci. Technol.
28
,
074001
(
2013
).
18.
M.
Ťapajna
,
S. W.
Kaun
,
M. H.
Wong
,
F.
Gao
,
T.
Palacios
,
U. K.
Mishra
,
J. S.
Speck
, and
M.
Kuball
,
Appl. Phys. Lett.
99
,
223501
(
2011
).
19.
C. G.
Van de Walle
,
J. Appl. Phys.
95
,
3851
(
2004
).
20.
J.
Åhman
,
G.
Svensson
, and
J.
Albertsson
,
Acta Crystallogr., Sect. C Cryst. Struct. Commun.
52
,
1336
(
1996
).
21.
T.
Oshima
,
N.
Arai
,
N.
Suzuki
,
S.
Ohira
, and
S.
Fujita
,
Thin Solid Films
516
,
5768
(
2008
).
22.
M.-Y.
Tsai
,
O.
Bierwagen
,
M. E.
White
, and
J. S.
Speck
,
J. Vac. Sci. Technol. A
28
,
354
(
2010
).
23.
Y.
Asaoka
,
J. Cryst. Growth
251
,
40
(
2003
).
24.
K.
Sasaki
,
M.
Higashiwaki
,
A.
Kuramata
, and
T.
Masui
,
J. Cryst. Growth
378
,
591
(
2013
).
25.
J.
Olivier
and
R.
Poirier
,
Surf. Sci.
105
,
347
(
1981
).
26.
K.
Irmscher
,
M.
Naumann
,
M.
Pietsch
,
Z.
Galazka
,
R.
Uecker
,
T.
Schulz
,
R.
Schewski
,
M.
Albrecht
, and
R.
Fornari
,
Phys. Status Solidi
211
,
54
(
2014
).
27.
N.
Ishizawa
,
T.
Miyata
,
I.
Minato
,
F.
Marumo
, and
S.
Iwai
,
Acta Crystallogr.
B36
,
228
(
1980
).
28.
M.
Marezio
,
Acta Crystallogr.
20
,
723
(
1966
).
29.
M.
Mizuno
,
T.
Yamada
, and
T.
Noguchi
,
Dainippon Yogyo Kyokai Zasshi
83
,
175
(
1975
).
30.
D. D.
Edwards
,
P. E.
Folkins
, and
T. O.
Mason
,
J. Am. Ceram. Soc.
80
,
253
(
1997
).
31.
A. L.
Jaromin
and
D. D.
Edwards
,
J. Am. Ceram. Soc.
88
,
2573
(
2005
).
32.
V. G.
Hill
,
R.
Roy
, and
E. F.
Osborn
,
J. Am. Ceram. Soc.
35
,
135
(
1952
).
33.
T.
Oshima
,
T.
Okuno
,
N.
Arai
,
Y.
Kobayashi
, and
S.
Fujita
,
Jpn. J. Appl. Phys.
48
,
070202
(
2009
).
34.
H.
Okumura
,
M.
Kita
,
K.
Sasaki
,
A.
Kuramata
,
M.
Higashiwaki
, and
J. S.
Speck
,
Appl. Phys. Express
7
,
095501
(
2014
).
35.
K.
Sasaki
,
M.
Higashiwaki
,
A.
Kuramata
, and
T.
Masui
,
J. Cryst. Growth
392
,
30
(
2014
).
36.
J. M.
LeBeau
,
R.
Engel-Herbert
,
B.
Jalan
,
J.
Cagnon
,
P.
Moetakef
,
S.
Stemmer
, and
G. B.
Stephenson
,
Appl. Phys. Lett.
95
,
142905
(
2009
).
37.
S.
Keller
 et al,
J. Appl. Phys.
103
,
033708
(
2008
).
You do not currently have access to this content.