J. M. Lee
1, J. Y. Chang
1,
K. I. Lee
1, S. H. Han
1,
H. J. Kim
1,
Wooyoung. Y. Lee1* (
),
M. C. Park
2, K. S. Huh
2,
and J. M. Myoung
2
1Nano Device Research Center, Korea Institute of Science
and Technology,
POB 131, Seoul, 130-650, Korea.
2Information & Electronic Materials Research Laboratory,
Department of Materials Science and Engineering, Yonsei University,
134 Shinchon-Dong, Seoul 120-749, Korea.
*Tel.: 82-2-958-5428, Fax: 82-2-958-6851.
We present the crystal structures, magnetic and magnetotransport
properties of
epitaxial (Ga1-xMnx)N films with low Mn concentration
(x = 0.06 - 0.5 %)
grown by plasma-enhanced molecular beam epitaxy (PEMBE). Transmission
electron microscopy
(TEM) studies revealed that Mn ions substitute for Ga ions
in the epitaxial structure,
leading to the expansion of lattice parameter a of the
hexagonal (wurtzite) structure.
Ferromagnetic ordering for the GaMnN is clearly seen in the
temperature range 4 - 300K. The M-T curves were fitted with
theoretical equations based on the mean field theory
in order to estimate Curie temperature (Tc), providing
Tc ~ 550K and Tc ~ 700K,
respectively, for the (Ga,Mn)N films with
x = 0.16% and x = 0.50%. Temperature
dependence of sheet resistance is found to show negative
magnetoresistance (
R/R =
20%) in the temperature range 4 -300K, indicative of
ferromagnetic semiconducting
(Ga,Mn)N films. Our results demonstrate that a (Ga,Mn)N film with low Mn
concentration is a ferromagnetic single-phase solid solution without
secondary phases
or clusters, suggesting the possibility of applying for spintronic
devices.
