Quantum Dot Infrared Photodetectors Based on Structures with Potential Barriers: Modeling and Optimization
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It is known that major restrictions of room-temperature semiconductor photodetectors and some other optoelectronic devices are caused by short photoelectron lifetime, which strongly reduces the photoresponse. Detectors based on nanostructures with potential barriers have the strong potential to overcome the limitations in quantum well photodetectors due to various possibilities for engineering of specific kinetic and transport properties. Here I review photocarrier kinetics in traditional quantum dot infrared photodetectors and present results of the investigations related to the quantum-dot (QD) structures with potential barriers created around dots and with collective barriers surrounding groups of quantum dots (planes, clusters etc). To optimize the photodetectors based on QD structures, I develop and exploit a model of the room-temperature QD photodetector. Using Monte-Carlo simulations, I investigate photoelectron capture and transit processes, as functions of selective doping of a QD structure, its geometry, and applied electric field. The simulation results demonstrate that the capture processes are substantially suppressed by the collective potential barriers around the groups of QDs. Detailed analysis shows that the effects of the electric field can be explained by electron heating, i.e. field effects become significant, when the shift of the electron temperature due to electron heating reaches the barrier height. Besides manageable photoelectron kinetics, which allows one to employ QDIP as an adaptive detector with changing parameters, the advanced QD structures will also provide high coupling to radiation, low generation-recombination noise, and high scalability.