Epitaxial growth of InN on (0001) sapphire with an AlN buffer layer was stu
died by migration-enhanced epitaxy, which is composed of an alternative sup
ply of pure In atoms and N-2 plasma. A series of samples were prepared with
different substrate temperatures ranging from 360 to 590 degrees C. As-gro
wn films were characterized by x-ray diffraction (XRD), reflective high-ene
rgy electron diffraction, atomic-force microscopy (AFM), and Hall measureme
nts. Both XRD theta-2 theta and omega scans show that the full width at hal
f maximum of the (0002) peak nearly continuously decrease with increasing g
rowth temperature, while InN grown at 590 degrees C shows the poorest surfa
ce morphology from AFM. It is suggested that three-dimensional characteriza
tion is necessary for an accurate evaluation of the quality of the InN epil
ayer. Hall mobility as high as 542 cm(2)/V s was achieved on film grown at
similar to 500 degrees C with an electron concentration of 3x10(18) cm(-3)
at room temperature. These results argue against the common view that nitro
gen vacancies are responsible for the high background n-type conductivity o
f InN. To illuminate the relationship between Hall mobility and carrier con
centration, the electrical properties of all InN films grown recently were
summarized. (C) 2000 American Institute of Physics. [S0003-6951(00)00942-6]
.