We present epitaxial growth, structures, magnetization, magneto-transport, and magneto-optic properties of (GaMn)As thin films and (GaMn)As/AlAs superlattice heterostructures grown by molecular beam epitaxy (MBE) on GaAs substrates. (Ga1-xMnx)As is a new class of III-V based magnetic alloy semiconductor grown by low temperature MBE, which contains a large amount of Mn atom (Mn concentration x up to 8%) far above the equilibrium solubility of Mn in GaAs. The feasibility of preparing such a m-V based magnetic semiconductor and its heterostructures gives a new degree of freedom in the materials design of III-V systems, offering new opportunities to explore spin-related phenomena as well as potential device applications using both magnetic and electronic/optical functions in III-V semiconductors.