AlN nucleation and buffer layers have been grown with different AlN flux ratio by molecular beam epitaxy on sapphire. Thick AlN on top of a nucleation layer grown with AlN flux ratio=1.0 exhibited deep hexagonal holes (diameter 100–200 nm, density 109cm2). Investigation of the nucleation layer surface revealed that the holes were formed already during the nucleation. The formation of holes in AlN buffer layers could be avoided by using a N-rich (AlN=0.5) nucleation layer. It is demonstrated that the holes in AlN buffer layers can be effectively avoided choosing a N-rich nucleation layer growth and then switch to AlN flux ratio =1.0 for buffer layer growth. The two-step AlN growth gave high quality AlN, with excellent crystalline quality and smooth surface.

1.
J.
Hwang
,
W. J.
Schaff
,
B. M.
Green
,
H.
Cha
, and
L. F.
Eastman
,
Solid-State Electron.
48
,
363
(
2004
).
2.
N.
Iizuka
,
K.
Kaneko
, and
N.
Suzuki
,
Electron. Lett.
40
,
962
(
2004
).
3.
H. M.
Ng
,
T. D.
Moustakas
, and
S. N.G.
Chu
,
Appl. Phys. Lett.
76
,
2818
(
2000
).
4.
C. T.
Foxon
and
O. H.
Hughes
,
J. Mater. Sci.: Mater. Electron.
9
,
227
(
1998
).
5.
K.
Jeganathan
,
X.-Q.
Shen
,
T.
Ide
,
M.
Shimizu
, and
H.
Okumura
,
Jpn. J. Appl. Phys., Part 1
41
,
4454
(
2002
).
6.
C. F.
Zhu
,
J. Q.
Xie
,
W. K.
Fong
, and
C.
Surya
,
Mater. Lett.
57
,
2413
(
2003
).
7.
E. C.
Piquette
,
P. M.
Bridger
,
R. A.
Beach
, and
T. C.
McGill
,
MRS Internet J. Nitride Semicond. Res.
4S1
,
G3
77
(
1999
).
8.
S. K.
Davidsson
,
J. F.
Fälth
,
X. Y.
Liu
, and
T. G.
Andersson
,
J. Appl. Phys.
98
,
016109
(
2005
).
9.
G.
Koblmueller
,
R.
Averbeck
,
L.
Geelhaar
,
H.
Riechert
,
W.
Hosler
, and
P.
Pongratz
,
J. Appl. Phys.
93
,
9591
(
2003
).
10.
J. R.
Heffelfinger
,
D. L.
Medlin
, and
K. F.
McCarty
,
J. Appl. Phys.
85
,
466
(
1999
).
You do not currently have access to this content.