Short-wavelength infrared tuneable filters on HgCdTe photoconductors

The design, micro-fabrication, and electronic and optical performance of a tuneable short-wavelength infrared Fabry-Pérot microresonator on a mercury cadmium telluride photoconductor is presented. The maximum processing temperature of 125 degrees C has negligible effect on the electronic and optical performance of photoconductor test structures. Maximum responsivity, effective carrier lifetime and detectivity are 60x103 VW-1, 2x10-5 s and 8x1010 cmHz1/2W-1, respectively. The maximum effective carrier lifetime and specific detectivity are in good agreement with the theoretical maxima. Uncooled device operation is possible since responsivity is observed not to improve with thermo-electric cooling. Spectral tuning of the micro-filters is demonstrated over the wavelength range 1.7 to 2.2 mum using drive voltages up to 8 V, with the full-width-half-maximum of the resonance approximately 100 nm. Membrane deflection can be up to 40% of the cavity width.