Low strain multiple stack quantum dot infrared photodetectors for multispectral and high resolution hyperspectral imaging

摘要

Quantum dot infrared photodetectos (QDIP) have received considerable interest for over a decade due to their sensitivity to normal incidence radiation and long excited carrier lifetimes[1]. A dot-in-a-well (DWELL) QDIP structure consisting of an InGaAs well between the InAs dot and GaAs barrier can be used to increase the quantum dot density and decrease thermionic emission by lowering the ground state of the quantum dot [2]. At present, QDIPs are limited by a relatively small absorption volume leading to a low quantum efficiency compared to quantum well infrared photodetectors and Cadmium Mercury Telluride based devices. It is challenging to increase the absorption volume by growing a large number of InGaAs-GaAs DWELL stacks due to the lattice mismatch between GaAs and InGaAs causing strain to build up through the device, leading to greatly increased dark currents. The strain build up can be decreased significantly by reducing the width of the InGaAs well and introducing lattice matched GaAs wells and AlGaAs barriers allowing a greater number of DWELL stacks to be grown [3].