Photoluminescence study of the excitation power dependence of the peak intensities of an asymmetric double quantum well

We present the results of a study of the dependence of the emission intensities of the excitonic peaks of a II-VI asymmetric double quantum well (ADQW) system at low temperature (19 K). The ADQW heterostructure is based on two CdSe ultrathin quantum wells (UTQWs) grown by atomic layer epitaxy with nominal coverages of 2 and 3 monolayers (MLs) and separated by a 10 nm ZnSe barrier. The excitation was produced by the 442 nm line of a HeCd laser. The photoluminescence spectra presents two peaks which change their relative intensities with the excitation power. To analyze the experimental results, we assumed a power law intensity dependence of the type I(w) = Awk, where A is a constant, w is the excitation power. For the 3 MLs CdSe UTQW we observed a linear dependence, whereas for the 2 MLs UTQW we obtained a superlinear dependence with k ∼ 1.3. At the lower excitations, the 3 MLs CdSe UTQW presented higher intensity. With increasing power the peak intensity of the narrow UTQW increased faster than that of th...