Investigation for optoelectronic characteristics and imaging performance of InAs quantum dot covered with In 0.1 Ga 0.9 As/GaAs multilayer based focal plane array

We report on a structure prepared by metalorganic chem- ical vapor deposition and molecular beam epitaxy techniques in- corporated with a standard process of compound semiconductor to achieve In0.1Ga0.9As/InAs/In0.1Ga0.9As quantum dot infrared photodetec- tor (QDIP)-based focal plane array. For investigating the mechanism of carrier transport and optoelectronic behavior, the photoresponse spec- tra and dark current were measured in agreement with the theoretical simulations. Furthermore, a model is proposed with the systematic anal- yses and explained for designing high-performance QDIPs based on the calculations of thermal activation energy and detectivity. For QDIP pho- toresponse measurements, the photovoltaic photoresponse is achieved, which can be attributed to the asymmetric morphology of quantum dot epitaxy. With increasing bias, the photoresponse spectra exhibit a red- shift due to band bending that generates a thinner triangle barrier which increases the escape possibility of the excited carriers situated at lower excited-state levels. The trapezoid-edged scheme enhances infrared cou- pling and increases the photoresponse intensity. A single-sided gradient AlxGa1-xAs (x = 0.25→0) barrier can suppress the dark-current under bias efficiently. The infrared imaging performance of InGaAs QDIP based on 320×256 FPA is also demonstrated in this paper. C 2011 Society of Photo-