Modified quantum-well infrared photodetector designs for high-temperature and long-wavelength operation

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Abstract
A principal concern with the performance of GaAs/AlGaAs multiple quantum well long- wavelength detectors is obtaining high detectivity at relatively high temperatures. We have fabricated GaAs/AlGaAs quantum well infrared photodetectors (QWIPs) with graded barrier regions by varying the aluminum concentration during the barrier growth to improve high temperature performance. The effect of barrier grading has been characterized by the measurement of dark current and responsivity, leading to an evaluation of the temperature dependent detectivity. Detectivity of 2 X 109 cm(root)Hz/W at 100 K has been measured on graded barrier QWIPs. We also report on the investigation of QWIPs with cut- off wavelengths ((lambda) c) greater than 12 micrometers . A QWIP with (lambda) c approximately 13.8 micrometers was grown with peak responsivity (Rp) of 1.2 A/W at 10 K. Both Rp and (lambda) c were weakly bias dependent. The maximum detectivity of 6 X 1012 cm(root)Hz/W was at 10 K at 11.7 micrometers and (lambda) c equals 14.5 micrometers .

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