A resonant cavity enhanced detector (RCED) sensitive at 4.4μ m wavelength has been realized with lead-chalcogenide narrow band gap materials grown on a Si(l 1 1) substrate. It consists of a resonant cavity containing the thin Pb1-yEuySe infrared detector and a Pb1-xEuxSe (x> y) spacer layer. The bottom Bragg mirror is formed by 2 pairs of λ/4 Pb1-xEuxSe/BaF2 stacks, while the top mirror consists of Ph which acts in addition as a blocking contact forming a photovoltaic detector. All layers are grown by solid source molecular beam epitaxy, and illumination is through the substrate. The spectral linewidth is below 1%, while quantum efficiency (without AR coating of the substrate) is as high as 32%. Operation temperature was up to about 150 K. This seems to be the first time that a RCED with a single dominant narrow detection line of high quantum efficiency has been realized in the mid IR range. © 2005 Elsevier B.V. All rights reserved.