Photodetectors on structures with vertically correlated dot clusters

Long photocarrier lifetime is a key issue for improving of room-temperature infrared photodetectors. Detectors based on nanostructures with quantum dot clusters have the strong potential to overcome the limitations in quantum well detectors due to various possibilities for engineering of specific kinetic and transport properties. Here we review photocarrier kinetics in traditional QDIPs and present results of our investigations related to the QD structures with vertically correlated dot clusters (VCDC). Modern technologies allow for fabrication of various VCDC with controllable parameters, such as the cluster size, a distance between clusters, dot occupation etc. Modeling of photocarrier kinetics in VCDC structures shows that the photocarrier capture time exponentially increases with increasing of the number of dots in a cluster. It also exponentially increases as the occupation of a dot increases. At the same time, the capture processes are weakly sensitive to geometrical parameters, such as the cluster size and the distance between clusters. Compared with ordinary quantum-dot structures, where the photoelectron lifetime at room temperatures is of the order of 1-10 ps, the VCDC structures allow for increasing the lifetime up to three orders of magnitude. We also study the nonlinear effects of the electric field and optimize operating regimes of photodetectors. Complex investigations of these structures pave the way for optimal design of the room-temperature QDIPs.