Temperature-dependent photoluminescence and contactless electroreflectance characterization of a Zn_xCd_1-xSe/Zn _x′Cd_y′Mg_1-x′-y′Se asymmetric coupled quantum well structure

Temperature-dependent photoluminescence (PL) and contactless electroreflectance (CER) were used to characterize a Zn_xCd _1-xSe/Zn_x′Cd_y′Mg _1-x′-y′Se asymmetric coupled quantum well (ACQW) structure in the range of 10-300 K. The PL peak position yielded information of the fundamental excitonic recombinations. A detailed analysis of the CER spectra led to the identification of various interband transitions. The intersubband transitions were then estimated and found to be in a good agreement with the previous report of Fourier-transform infrared absorption measurements. At low temperature, the PL spectra of the sample showed an asymmetric behavior with an exponential tail at the lower-energy side and were attributed to the localized excitonic recombinations due to potential fluctuations. Detailed study of the temperature dependence of the excitonic transition energies indicated that the main influence of temperature on the quantized transitions is through the temperature dependence of the band gap of the constituent material in the well.