FABRICATION OF ALAS/AL/ALAS HETEROSTRUCTURES BY MOLECULAR-BEAM EPITAXY AND MIGRATION ENHANCED EPITAXY

AlAs/Al/AlAs heterostructures are fabricated on (001)GaAs by molecular beam epitaxy (MBE) and migration enhanced epitaxy (MEE). The Al and successive AlAs layers are grown at room temperature by MBE and MEE, respectively, while the underlying AlAs layer is grown at 600-degrees-C by MBE. Single crystal Al layers are grown successfully. The epitaxy relationship of Al with the underlying AlAs layer is (011)[100]Al parallel-to (001)[110]AlAs. Detailed RHEED analysis elucidates the lattice relaxation processes of Al on AlAs as well as the growth process. It is suggested that the initially deposited 2(1) ML thick Al layers occupy sublattice sites in the AlAs lattice with the same lattice spacing as AlAs on As- (Al-) stabilized AlAs and that the lattice relaxation and the formation of the fcc Al lattice is initiated during deposition of the 3rd (2nd) layer on As- (Al-) stabilized AlAs. The top AlAs layer is single crystalline and grows in an island growth mode. The observed epitaxy relationship of AlAs on Al is (001)[110]AlAs parallel- to (011)[100]Al.