InN epilayers have been grown on GaAs(001)substrates by MBE at 500℃ under the N

2

pressure of 2.67×10

-2

Pa.During the growth

the In flux was varied from 3×10

14

to 24×10

14

atoms/cm

2

sec.The InN films were characterized by X-ray diffraction (XRD) and reflection high energy electron diffraction (RHEED) measurements.It is found that the cubic phase InN was grown at initial stage of growth

but the transition from cubic phase InN to hexagonal phase InN occurred with increase of the thickness of InN epilayer.The X-ray reciprocal space mapping (RSM) measurements show that the hexagonal phase InN whose

c

-axes are oriented in the GaAs

<

111

>

B direction is dominantly grown on (001) GaAs.