Reduced Dark Current With a Specific Detectivity Advantage in Extended Threshold Wavelength Infrared Detector

Reduced dark current leading to a specific detectivity (D*) advantage over conventional detectors for extended threshold wavelength (ET) detectors are reported in this article. For an infrared (IR) detector with a graded injector barrier and barrier energy offset, the measured dark current was found to agree well with theoretical fits obtained from a 3-D carrier drift model using the designed value of Δ = 0.40 eV (λ t = 3.1 μm) (where Δ = 1.24/λ t , Δ is the internal work function and λ t is the corresponding threshold wavelength), whereas the effective photoresponse threshold wavelength determined from the spectral response measurements corresponds to 13.7 μm at 50 K. However, for the conventional detectors, both the dark current and photoresponse threshold agree very well with the designed value of Δ. Comparing threshold wavelengths of an ET detector and a conventional detector, an advantage in D* is observed for ET detectors due to the strong reduction in dark current. Using this idea, standard threshold semiconductor detectors could be designed to operate as long wavelength detectors with a higher value of detectivity and dark current (corresponding to the original short-wavelength threshold).