XB(n)n and XB(p)p barrier detectors grown from IIIV materials on GaSb substrates have recently been shown to exhibit a low diffusion limited dark current and a high quantum efficiency. Two important examples are InAsSb/AlSbAs based XBnn devices with a cut-off wavelength of lambda(c)similar to 4.1 mu m, and InAs/GaSb Type II superlattice (T2SL) based XB(p)p devices, with lambda(c)similar to 9.5 mu m. The former exhibit background limited performance (BLIP) at F/3 up to similar to 175 K, which is a much higher temperature than observed in standard generation-recombination limited devices, such as InSb photodiodes operating in the same Mid Wave IR atmospheric window. The Long Wave IR (LWIR) T2SL XB(p)p device has a BLIP temperature of similar to 100 K at F/2. Using the k center dot p and optical transfer matrix methods, full spectral response curves of both detectors can be predicted from a basic knowledge of the layer thicknesses and doping. The spectral response curves of LWIR gallium free InAs/InAs1-xSbx barrier devices have also been simulated. These devices appear to have a lower quantum efficiency than the equivalent InAs/GaSb XB(p)p devices. (C) 2015 Elsevier B.V. All rights reserved.