Formation of rotation-induced superlattices and their observation by tunneling spectroscopy

We show that superlattices can be formed in the ternary and quaternary ln(GaAl)As alloys on InP by molecular beam epitaxy without mechanical shuttering. Periodic ordering is produced by rotation of the substrate through the naturally nonuniform distribution of beam fluxes at the rotating substrate. The growth rate and substrate rotation rate together determine the superlattice period which is measured by transmission electron microscopy and x-ray diffraction. Tunneling density-of-states measurements on resonant tunneling diodes, interpreted by a one-dimensional theoretical calculation of the miniband-structure, reveal the electrical properties of the superlattice.