  The microstructure of (In,Mn)As thin films grown using metalorganic vapor
phase epitaxy (MOVPE) was investigated to determine the origin of room
temperature ferromagnetism in these films. Transmission electron microscopy
(TEM) based techniques were used to investigate phase purity and compositional
homogeneity. Microanalysis of an In1-xMnxAs film with x = 0.01 and a Curie
temperature of 330 K exhibited a homogeneous distribution of Mn. High Mn
concentration films with x = 0.20 exhibited MnAs precipitates within the
(In,Mn)As matrix. The analysis indicates that room temperature ferromagnetic,
single-phase (In,Mn)As can be formed by MOVPE. The origin of ferromagnetism is
attributed to (In,Mn)As solid solution rather than distinct secondary Mn-rich
magnetic phase(s).
