Quantum well infrared photodetector (QWIP) technology is still the only thermal imaging sensor technology providing excellent pixel operability, uniformity and stability together with low production cost and insignificant 1/f noise. The main bottleneck of the standard QWIP technology is the low quantum efficiency and device gain inhibiting the utilization of the sensor for low background and/or high frame rate applications. This manuscript reports unusually high quantum efficiency observed in mid-wavelength infrared (MWIR) QWIPs constructed with solid-source molecular beam epitaxy grown thirty In0.83Ga0.17As quantum wells sandwiched between InP and GaInP barriers. Large area (300 x 300 mu m(2)) bound-to-continuum detectors with similar to 5.7 pm cutoff wavelength exhibited very broad (Delta lambda/lambda p = similar to 40%) responsivity spectrum together with impressively high peak absorption quantum efficiency of similar to 20% and a 78 K peak specific detectivity above 1 x 10(11) cmHz(1/2) /W with f/2 optics in the absence of diffraction grating. Even higher signal-to-noise ratio was observed in grating free small area ( 20 x 20 mu m(2)) detectors hybridized to a fan-out substrate. Considering the expected improvements in the quantum efficiency by confining the responsivity spectrum to the narrower (and useful) wavelength region in the MWIR band and utilization of diffraction grating, the results presented in this manuscript have considerable potential to open the door to reshape the QWIP technology.