Exciton resonances in ultrathin InAs/InP quantum wells

We have performed detailed optical measurements of ultrathin InAs/InP quantum wells grown by metal organic vapor phase epitaxy. Photoluminescence excitation spectra reveal the excitonic resonances associated with two- and three-monolayer thick InAs layers while polarization-dependent measurements clearly show the heavy- or light-hole nature of the resonances. These resonances, together with their emission bands, can be detected on the same sample, indicating the presence of well defined regions of different InAs layer thickness. We find that the energy position of the excitonic resonances cannot be reproduced by effective mass calculations based on the envelope function approximation. (C) 1999 American Institute of Physics. [S0003-6951(99)00510-0].