Optical Investigation of Critical Thickness and Interface Fluctuation in CdSe/ZnSe Strained Layer Superlattices Grown on InP

Abstract

Optical measurements are performed for CdSe n /ZnSe n strained layer superlattices with n =2 to 10 ML grown on InP substrates to investigate the structural property. The electron-heavy-hole transition is observed from all strained layer superlattices and the electron-light-hole transition is observed from strained layer superlattices with n larger than 6 ML by photoreflectance spectroscopy. The comparison of transition energy measured by photoreflectance and calculation results based on the transfer matrix reveals that the critical thickness for strain relaxation of the CdSe/ZnSe strained layer superlattice on InP is 8 to 10 ML. The photoluminescence peak energy exhibits blue shift with increasing temperature in the region of 12 to 40 K for n =4, 6, and 8 ML, while reflectance spectra reveal a monotonic red shift. The blue shift in the low-temperature region indicates the carrier localization originating due to interface fluctuation.