Responsivity and Lifetime of Resonant-cavity-enhanced HgCdTe photodetectors

Resonant cavity enhanced HgCdTe structures using absorbers only 75nm thick have been grown by molecular beam epitaxy, and photoconductors have been modelled and fabricated based on these structures. Responsivity has been measured and shows a peak responsivity of 8 10⁴ V/W for a 50 50 mum² photoconductor at a temperature of 200K. The measured responsivity shows good agreement with the modelled responsivity across the mid-wave infrared window (3-5mum). The measured responsivity is limited by surface recombination, which limits the effective lifetime to ap 15ns. The optical cut-off of the detector varies with temperature as modelled from 5.1 mum at 80K to 4.4 mum at 250K. There is strong agreement between modelled and measured peak responsivity as a function of temperature from 80-300K. The refractive index of CdTe used in the structures is investigated and is found to have a reduced refractive index