Diffraction-Grating-Coupled High Quantum Efficiency InP/InGaAs Quantum Well Infrared Photodetector Focal Plane Array

Quantum well infrared photodetector (QWIP) is still the sole field proven low-cost long-wavelength infrared photon sensor. We report an impressively high quantum efficiency of 31% in the pixels of a large format (640 × 512) grating-coupled InP/In_0.48Ga_0.52As QWIP focal plane array (FPA). The InP/InGaAs QWIP FPA with a cut-off wavelength of ~ 9 μm provided desirable characteristics at a temperature as high as 78 K. The noise-equivalent temperature difference of the FPA with f/2 optics is ~ 30 mK with an integration time as low as 1 ms at 67 K. We also present a thorough comparison of InP and GaAs-based QWIPs for long-wavelength infrared thermal imaging and shed light on the characteristic differences between these devices to be used as a guide for improving the performance of this important sensor technology. The results clearly indicate that the main limitations of the standard QWIP technology can be overcome through the utilization of alternative material systems and proper FPA processing techniques.