nBn Based Infrared Detectors Using Type-II InAs/(In,Ga)Sb Superlattices

摘要

The development of type-II InAs/(In,Ga)Sb superlattice (SL) detectors with nBn design for single-color and dual-color operation in MWIR and LWIR spectral regions are discussed. First, a 320 × 256 focal plane array (FPA) with cutoff wavelength of 4.2 urn at 77K with average value of dark current density equal to 1 × 10~(-7) A/cm~2 at V_b=0.7V (77 K) is reported. FPA reveals NEDT values of 23.8 mK for 16.3 ms integration time and f/4 optics. At 77K, the peak responsivity and detectivity of FPA are estimated, respectively, to be 1.5 AAV and 6.4 × 10~(11) Jones, at 4 μm. Next, implementation of the nBn concept on design of SL LWIR detectors is presented. The fabrication of single element nBn based long wave infrared (LWIR ) with λ_c～ 8.0 μm at V_b = +0.9 V and T= 100K detectors are reported. The bias dependent polarity can be exploited to obtain two color response (λ_(c1)～ 3.5 μm and λ_(c2)～ 8.0 μm) under different polarity of applied bias. The design and fabrication of this two color detector is presented. The dual band response (λ_(c1) ～ 4.5 μm and λ_(c2) ～ 8 μm) is achieved by changing the polarity of applied bias. The spectral response cutoff wavelength shifts from MWIR to LWIR when the applied bias voltage varies within a very small bias range (～100 mV).