Excitons in ultrathin InAs/InP quantum wells: Interplay between extended and localized states

We have performed detailed optical measurements of ultrathin InAs/InP quant um wells grown by metalorganic vapor phase epitaxy. Absorption and photolum inescence excitation spectra reveal the excitonic resonances associated wit h two- and three-monolayer-thick InAs layers. Photoluminescence spectra als o show an emission band at intermediate photon energies which is associated with excitons localized in thin InAs quantum dots. Polarization-dependent measurements clearly show the heavy-hole or light-hole nature of the quantu m well resonances. Such an identification of both type of transitions provi des a test for electronic structure models. We find that the energy positio ns of the excitonic transitions in ultrathin InAs/InP quantum wells are not consistent with calculations based on the envelope function model. (C) 200 0 American Vacuum society. [S0734-2101(00)01903-5].