Progress in enhanced quantum well infrared photodetectors

This paper reports recent results from a novel approach for fabricating RI detectors from GaAs/AlGaAs multiple quantum well (MQW) materials. It involves the fabrication of quantum-well IR photodetectors (QWIPs) by patterning a 3D diffractive resonant optical cavity into the MQW structure. This approach, called the Enhanced QWIP (EQWIP), enables highly effective optical coupling into the MQW material resulting in narrow spectral response, improved detector quantum efficiency (QE), reduced dark currents, and improved photoconductive gain. EQWIP arrays operating in the 8-10 μm spectral band are reported in this paper. The peak response wavelength of the detectors, within the absorption band of the MQW material, is tuned by controlling the dimensions of the resonant structure. EQWIPs with peak spectral response at 8.6 μm exhibit peak responsivity as high as 2.6 A/W and quantum efficiency (QE) as high as 57%. Total conversion efficiency is as high as 35%. The background limited, peak detectivity measured at 9.0μm and 55 K with a 295 K background at f/2.5 is greater than or equal to 1 × 1011 cm-Hz0.5/W.