More Accurate Quantum Efficiency Damage Factor for Proton-Irradiated, III-V-Based Unipolar Barrier Infrared Detectors

Ongoing studies to characterize and improve the radiation tolerance of the quantum efficiency (QE) in III-V-based, unipolar barrier infrared detectors, such as nBn's, require accurate knowledge of the detector QE damage factor. Here, results of such studies are described which demonstrated that a QE damage factor determined from the slope of the apparent linear relationship between inverse QE and proton fluence was more accurate than the previous method. Comparatively, the new approach did not require truncating the fitting range and it more clearly demonstrated the expected monotonically decreasing relationship between QE damage factor and relative amount of absorber layer grading in nBn detectors. Simulations were then done which supported this finding. Results from a similar study of HgCdTe photodiodes indicated an identical linear behavior which then abruptly saturated at higher proton fluence. Additional simulation suggested photo-collection here also relied on drift, which thereby limited the total effects of displacement damage on QE.