  We report the heteroepitaxy of single crystal thin films of Bi2Se3 on the
(111)B surface of GaAs by molecular beam epitaxy. We find that Bi2Se3 grows
highly c-axis oriented, with an atomically sharp interface with the GaAs
substrate. By optimizing the growth of a very thin GaAs buffer layer before
growing the Bi2Se3, we demonstrate the growth of thin films with atomically
flat terraces over hundreds of nanometers. Initial time-resolved Kerr rotation
measurements herald opportunities for probing coherent spin dynamics at the
interface between a candidate topological insulator and a large class of
GaAs-based heterostructures.
