Quantum dot based infrared focal plane Arrays

In the past decade, there has been active research on infrared detectors based on intersubband transitions in self-assembled quantum dots (QDs). In the past two years, at least four research groups have independently demonstrated focal plane arrays based on this technology. in this paper, the. progress from the first raster scanned image obtained with a QD detector to the demonstration of a 640 x 512 imager based on self-assembled QDs is reviewed. in particular, emphasis will be placed on a novel quantum clots-in-a-well (DWELL) design, which represents a hybrid between a conventional quantum-well infrared photodetector (QWIP) and a quantum-dot infrared photodetector (QDIP). In the DWELL detectors, the active region consists of InAs quantum dots embedded in an InGaAs quantum well. Like QDIPs, the DWELL detectors. have 3-D confinement and display normal incidence operation while demonstrating reproducible dial-in recipes for control over the operating wavelength, like QWIPs. Moreover, the DWELL detectors also have demonstrated bias-tunability and multi-color operation in the midwave infrared (MWIR, 3-5 mu m), long-wave infrared (LWIR, 8-12 mu m), and very long wave infrared (VLWIR, > 14 mu m) regimes. Recently midformat 320 x 256 and 640 x 512 focal plane arrays (FPAs) with an NETD of 40 mK at T = 60 K have been reported. The paper will conclude with a perspective on the future directions on the research on QDIP FPA including enhanced functionality and higher operating temperatures.