The
Composition Pulling Effect in MOVPE Grown InGaN on GaN and AlGaN and its TEM
Characterization
K. Hiramatsu
Mie University
Y. Kawaguchi, M. Shimizu, N. Sawaki
Nagoya University
T. Zheleva, Robert F. Davis
North Carolina State University
H. Tsuda, W. Taki, N. Kuwano, K. Oki
Kyushu University
This invited article was received on Tuesday, March 25, 1997 and
accepted on Tuesday, May 13, 1997. Abstract
InGaN films have been grown on GaN and AlGaN epitaxial layers by
metalorganic vapor phase epitaxy. The "composition pulling effect" during the
initial InGaN growth stages has been studied as a function of the lattice
mismatch between the InGaN and the underlying epitaxial layer. The crystalline
quality of the InGaN is good near the InGaN/GaN interface and the composition
is close to that of GaN. However, with increasing InGaN film thickness, the
crystal quality deteriorates and the indium mole fraction increases. The
composition pulling effect becomes stronger with increasing lattice mismatch.
It is suggested that indium atoms are excluded from the InGaN lattice during
the early growth stages to reduce the deformation energy from the lattice
mismatch. TEM observations of the InGaN/GaN structure reveal that the
degradation of the crystalline quality of InGaN films grown on GaN is caused by
pit formation which arises from edge dislocations propagating through the InGaN
film from the underlying GaN.
