Study of photo-degradation in II-VI heterostructures using n-i-n photoconductors

In this work, photo-degradation in ZnSe/Zn_0.67Cd_0.33Se multiple quantum well (MQW) structures was studied using photoluminescence of undoped structures and photocurrent of n-i-n photoconductors. The photoluminescence measurements were performed with respect to sample temperature, pump power and pump wavelength. The dependence of the measured photo-degradation from optical pumping on each of these parameters was quantified. To further understand this problem, n-i-n photoconductors were fabricated from these materials. Using these photoconductors, the formation of non-radiative recombination sites was monitored using standard photocurrent experiments. Moreover, the photocurrent generated was investigated as a function of applied voltage and excitation wavelength. The magnitude of the photocurrent decayed in a similar fashion to the photoluminescence measurements. Furthermore, n-i-n photoconductors fabricated from bulk material, as opposed to MQW structures, showed no evidence of photo-degradation. This implies that the photo-degradation is due to the interaction of the two constituent material systems.