A IDCA system combining thermo-electric cooler (TEC) and an internal nBn photo-detector having a photo absorbing layer comprising an n-doped semiconductor exhibiting a valence band energy level; and a contact layer comprising a doped semiconductor. A barrier layer is disposed between the photo absorbing layer and the contact layer, the barrier layer exhibiting a valence band energy level substantially equal to the valence band energy level of the doped semiconductor of the photo absorbing layer; the barrier layer exhibiting a thickness and a conductance band gap sufficient to prevent tunneling of majority carriers from the photo absorbing layer to the contact area and block the flow of thermalized majority carriers from the photo absorbing layer to the contact area. Alternatively, a p-doped semiconductor is utilized, and conductance band energy levels of the barrier and photo absorbing layers are equalized.