Evidence of Interface Roughness Correlation in CdTe/(Cd, Zn)Te Quantum Wells

The homogeneous and inhomogeneous linewidth of excitonic transitions characterize the interfacial quality of QW structures.1 We measured the inhomogeneous linewidth Γ inh by cw photoluminescence (PL) and reflectivity (REF) spectra on a series of undoped single CdTe/Cdl-xZnxTe QW’s with x = 0.16 – 0.18 and thickness L between 18 A and 112 A. We determined the zero-exciton-density- and zero-temperature-limit of the homogeneous linewidth Γ hom by density and temperature dependent degenerate-four-wave-mixing (DFWM) experiments. In these experiments, a mode locked Ti:Sapphire laser operating at 76 MHz was used. For a selective, resonant excitation of the exciton transition the bandwidth of 120-fs pulses was reduced to a pulsewidth of 4 meV, corresponding to 800 fs.