Determination of the roughness of heteroboundaries from photocurrent spectra of short-period AlAs/GaAs superlattices

Photocurrent spectroscopy is used to study the nature of the roughness of heteroboundaries in (AlAs)(m)/(GaAs)(n) short-period superlattices (m = 3 - 5, n = 10 - 13) grown by molecular-beam epitaxy. The formation of minibands broadens the optical spectra of superlattices in comparison with isolated quantum wells; therefore to analyze the degree of perfection of the boundaries we used the decay of the minibands into a series of discrete Wannier-Stark levels in an electric field parallel to the superlattice axis. Exciton lines were observed in the photocurrent spectra in an electric field corresponding to direct and indirect (in space) transitions between that even in the better structures, in additions to monotonic variations of the thickness of the layers over area, roughness in the heteroboundaries one monolayer in height are present with characteristic lateral dimension not exceeding 10 nm. (C) 1997 American Institute of Physics.