Comparison of Long-Wave Infrared Quantum-Dots-in-a-Well and Quantum-Well Focal Plane Arrays

This paper reports on a comparison between a commercially available quantum-well infrared focal plane array (FPA) and a custom quantum-dot (QD)-in-a-well (DWELL) infrared FPA in the long-wave infrared (LWIR). The DWELL detectors consist of an active region composed of InAs QDs embedded in $ hbox{In}_{.15}hbox{Ga}_{.85}hbox{As}$ quantum wells. DWELL samples were grown using molecular beam epitaxy and fabricated into 320 $times$ 256 pixels FPA with a flip-chip indium bump technique. Both the DWELL and QmagiQ commercial quantum-well detector were hybridized to an Indigo ISC9705 readout circuit and tested in the same camera system. Calibrated blackbody measurements at a device temperature of 60 K with LWIR optics yield a noise equivalent change in temperature of 17 mK and 91 mK for quantum-well and DWELL FPAs operating at 0.95- and 0.58-V biases, respectively. The comparison of the DWELL and quantum-well FPA when imaging a 35 $^{circ}hbox{C}$ black body showed that the DWELL had a signal-to-noise ratio of 124 while the quantum-well FPA showed 1961. As well, the quantum-well FPA showed a higher collection efficiency of 1.3 compared to the DWELL.