We report on the initial growth mechanism of GaAs on vicinal Si(110) s
ubstrates grown by molecular beam epitaxy, for the first time, while c
onsidering the effects of the substrate off-angle and direction on the
crystalline quality of GaAs films. The quality was improved with an i
ncrease of the off-angles, and was strongly influenced by the off-dire
ction. The off-direction towards the [001] was better than that toward
s [1 $($) over bar$$ 10] for obtaining high quality films. We believe
that this is related to a difference in the step structure. We infer f
rom the results of reflection high-energy electron diffraction, double
-crystal X-ray diffraction, atomic force microscopy and plan view tran
smission electron microscopy that GaAs films on vicinal Si(110), with
off-angles of 5 degrees-7 degrees towards the [001] direction, grow re
gularly along the [1 $($) over bar$$ 10] step edges at mono-atomic lay
er steps. On these step edges, the films grow to a thickness of 3 nm i
n a step flow like mode, and connect with each other through step-bunc
hing at large steps having a height of 5 nm.