Far Infrared Mercury-Cadmium-Telluride Photoconductive Detectors

摘要

Measurements of the excess-electron lifetime, electron concentration, electron mobility, and photoconductive spectral response were performed on HgCdTe alloys with 17 to 24% CdTe between 5 K and 300 K. The temperature dependence of the electron concentration was well fitted by the Kane band model using energy gap determinations from photoconductivity measurements and assuming donor levels with ionization energies between 0 and 7 meV. The level of sample compensation was determined from fits to the electron mobility, which was limited by impurity scattering below 80 K. The temperature dependence of the excess-electron lifetime was analyzed with a photoconductivity theory which includes intrinsic and defect recombination mechanisms and effects from the surface recombination velocity and incident background photon flux. For all sample compositions, a characteristic dependence of electron lifetime on temperature was observed. Above 100 K the lifetime decreases with temperature and is limited by intrinsic Auger recombination. Below 100 K the lifetime decreases with decreasing temperature because of Shockley-Read recombination. A large increase in the lifetime below 40 K is observed and attributed to minority carrier trapping.