InAsSb ternary alloy is potentially capable of operating at the longest cut-off wavelength (about 9 μm at 77 K) in the entire III-V family. Recently, there has been a considerable progress in development of the InAsSb focal plane arrays. The high operation temperature conditions were successfully achieved with AIIIBV unipolar barrier structures including InAsSb/AlAsSb material system. In this paper, the performance of medium wavelength infrared (MWIR) InAsSb-based nBnnn+ detectors, called also "bariodes", is examined theoretically taking into account thermal generation governed by the Auger and radiative mechanisms. In our model, the heterojunction barrier-active region (absorber) is assumed to be decisive as the contributing dark current mechanism limiting detector's performance. Since there is no depletion layer in the active layer of such devices, generation-recombination and trap assisted tunneling mechanisms are suppressed leading to lower dark currents in bariode detectors in comparison to standard diodes. Detailed analysis of the detector’s performance (such as dark current, RA product, and current responsivity) versus bias voltage and operating temperatures are performed pointing out optimal working conditions. The theoretical predictions of bariode parameters are compared with experimental data published in the literature. Finally, the bariode performance is compared with standard p+-on-n InAsSb photodiodes operated at room temperature with the same bandgap wavelength.