Sensitivity assessment of 4.8 μm cutoff GaInAsSbBi nBn photodetectors for mid-wave infrared sensing applications

GaInAsSbBi nBn photodetectors are grown lattice-matched on GaSb by molecular beam epitaxy. Device structures exhibit smooth surface morphologies, minority carrier lifetimes on the order of 0.5 μs at 130 K, and demonstrate a 4.8 μm wavelength cutoff, a 0.3 μm cutoff extension to a Bi-free GaInAsSb nBn counterpart. Dark current and quantum efficiency measurements of the nBn provide a 3–5 μm in-band shot-noise-limited noise-equivalent irradiance that is ∼12× the Rule 07 reference in which unity quantum efficiency is assumed. The analysis of the device behavior indicates that detector performance is limited by the valence band alignment at the barrier/active region interface, which imparts a barrier to photocollection at lower operating biases and leads to a significant reduction in the quantum efficiency with decreasing temperature. While more investigation is required to optimize the valence band alignment, the results in these detectors indicate that performance comparable to Rule 07 is within reach.