Large Format InAsSb XBn detectors operated at 150K

Over the past few years, High Operating Temperature (HOT) photon detectors have been developed at SCD, based on the patented XBn architecture. These devices incorporate a narrow bandgap active layer (AL) of InAs_1-x­Sb_x and a wide band gap barrier layer (BL) of AlSb_1-y­As_y . Both layers are doped n-type in order to prevent depletion of the AL at the operating bias, leading to a very low diffusion limited dark current. The AL material has a cut-off wavelength of 4.2 mm at 150 K which is very well matched to the region of the mid-wave infrared (MWIR) atmospheric window with the highest transmission coefficient. Dark currents are equal to those predicted by MCT Rule 07[i], and the detectors exhibit background limited performance (BLIP) up to ~175K at F/3.

In this work, we present a brief review of the operating principles and radiometric performance of the XBn detector, and demonstrate a phenomenological model that is able to predict the detector dark current and quantum efficiency (QE) as a function of the AL thickness and doping. It is shown how too much doping in the AL leads to a reduction of the QE due to the Moss Burstein effect. We also present measurements of the modulation transfer function (MTF) for different detector pitch sizes and relate these to low values of pixel crosstalk.

The HOT XBn architecture has very high pixel operability at typical operating temperatures of 150 K, which enables the production of Focal Plane Array (FPA) detectors with a low Size, Weight and Power (SWaP) and with large formats up to several megapixels. Results will be demonstrated for 15 µm detectors which are already in production and for the new generation of 10 µm pitch detectors which are in advance stage of development.

[i] E. Tennant, “Rule 07 Revisited: Still a Good Heuristic Predictor of …?” J. Electron. Mat. 39, 1030 (2010)