Interband transitions in [001]-(GaP)1(InP)m superlattices

We study the optical interband transitions of [001]-(GaP)(1)(InP)(m) monolayer superlattices on (001) InP for m = 5, 14, 27 and 51 using spectroscopic ellipsometry for photon energies from 1 to 6 eV. Samples were grown by metal-organic vapor phase epitaxy. We determine the InP-like E-0, E-0, + Delta(0), E-1, E-1 + A(1), and E-2 transitions from lineshape analysis of the pseudo dielectric function <epsilon>, The E-0 and E-0 + Delta(0) interband transitions depend on in due to effective alloying, strain, and symmetry reduction upon the superlattice period. Empirical pseudopotential calculations for superlattices with in = 1,...,14 confirm the observed dependence of the E-0 transition on the superlattice period. We further discuss our theoretical findings of type-II alignment for electrons and holes, which should be located within the GaP- and InP monolayers, respectively. (C) 2002 Elsevier Science B.V. All rights reserved.