Exciton resonances in ultrathin InAs/InP quantum wells

We have performed detailed optical measurements of ultrathin InAs/InP quant um wells grown by metal organic vapor phase epitaxy. Photoluminescence exci tation spectra reveal the excitonic resonances associated with two- and thr ee-monolayer thick InAs layers while polarization-dependent measurements cl early show the heavy- or light-hole nature of the resonances. These resonan ces, together with their emission bands, can be detected on the same sample , indicating the presence of well defined regions of different InAs layer t hickness. We find that the energy position of the excitonic resonances cann ot be reproduced by effective mass calculations based on the envelope funct ion approximation. (C) 1999 American Institute of Physics. [S0003-6951(99)0 0510-0].