The properties of a midinfrared photodetector, based on a lattice matched n-N In As0.91 Sb0.09 GaSb type-II heterostructure, were investigated. The relatively simple two layer structure shows very promising characteristics for sensitive and dual color infrared detection. I-V characteristics and spectral response were measured at the temperature range of 10-300 K. High zero-bias resistance area product R0 A of 2.5 cm2 was obtained at room temperature. The measured background limited infrared photodetection temperature was 180 K corresponding to 4.1 μm cutoff. Shot and Johnson noise limited detectivities corresponding to InAsSb absorption were measured to be 1.3× 1010 and 4.9× 109 cm Hz12 W-1 at 180 and 300 K, respectively. An enhanced optical response with gain larger than unity was observed below 120 K. Bias tunable dual color detection was demonstrated at all measured temperatures.