The influence of Sb content and dots size of InAs/GaAs_(1-x)Sb_x quantum dot on type I-type II band alignment and carrier dynamics

The band structure and carrier dynamics of InAs/GaAs_(1-x)Sb_x/GaAs quantum dots (QDs) are investigated by the eight-band model and by looking at the optical matrix elements of the envelope functions. Simulation solutions were obtained for different Sb concentrations in the cover layer and different QD heights. The results indicated that the conversion process from type I to type II caused by the Sb content could be divided into three stages: type I (less than 8%), the turning process (8%-14%), and type II (more than 14%). The influence of QD height on the wave function of carriers can be seen only in the second stage. It reverses the effect of Sb content by influencing the quantum confinement of hole states. Additionally, the potential radiation recombination channels are changed by these two factors. Unlike the first stage (where the ground-state transition is mainly channel), the first two hole levels and the first two electron levels are involved in radiation recombination in the second stage. So two recombination channels could be observed in the latter part of the second stage, which is consistent with the experimental results from the literature.