Radiometric characterization of an LWIR, type-II strained layer superlattice pBiBn photodetector

•We measured dark-current, photo-current, and noise spectrum on a LWIR pBiBn.•At 80 K, dark-current ranged from 20 to 80 mA/cm2.•At higher temperatures, SRH and diffusion current dominated at the operating bias.•The measured quantum efficiency at 7.9 μm was determined to be 22.9%.•The measured current noise was well above the expected shot noise.

Type-II Strained Layer Superlattice (T2SLS) infrared photodetectors have been in development over the last decade. T2SLS offers a theoretically longer Auger recombination lifetime than traditional mercury cadmium telluride (MCT), which presumably translates to infrared detectors with lower dark-current and higher operating temperatures. However, these improvements did not materialize due to the presence of Shockley–Read–Hall (SRH) defects in T2SLSs, which limits the recombination lifetime well below the Auger-limit. With the recent introduction of the pBiBn, and other similar unipolar barrier detectors, T2SLS material has seen renewed interest since these designs ideally eliminate the SRH-generation and surface currents while retaining the other potential advantages of T2SLS: reduced manufacturing cost, better availability of a durable state-side manufacturing base, ability to tune the cutoff wavelength, and better uniformity. Here, an electrical and optical characterization of a long-wave, pBiBn detector with a T2SLS absorber is presented. Dark-current, spectral response and optical response were measured as functions of temperature and bias. Activation energy was then determined as a function of bias from the dark-current measurements. Quantum efficiency was also determined as a function of bias from the optical response measurements. Additionally, noise spectrum measurements were taken as a function of bias.