  We report the growth, structural characterization, and transport properties
of the quantum anomalous Hall insulator Vy(BixSb1-x)2-yTe3 (VBST) grown on a
GaAs buffer layer by molecular beam epitaxy on a GaAs(111)A substrate. X-ray
diffraction and transmission electron microscopy show that the implementation
of a GaAs buffer layer improves the crystal and interface quality compared to
the control sample grown directly on an InP substrate. Both samples exhibit the
quantum anomalous Hall effect (QAHE), but with similar thermal stability
despite the different structural properties. Notably, the QAHE in the sample
grown on a GaAs buffer layer displays a significantly larger (almost double)
coercive field with a much smaller resistivity peak at the magnetization
reversal. Possible effects of the interface quality on the magnetic properties
of VBST and the QAHE are discussed.
