High-speed InSb photodetectors on GaAs for mid-IR applications

We report p-i-n type InSb-based high-speed photodetectors grown on GaAs substrate. Electrical and optical properties of photodetectors with active areas ranging from 7.06/spl times/10/sup -6/ cm/sup 2/ to 2.25/spl times/10/sup -4/ cm/sup 2/ measured at 77 K and room temperature. Detectors had high zero-bias differential resistances, and the differential resistance area product was 4.5 /spl Omega/ cm/sup 2/. At 77 K, spectral measurements yielded high responsivity between 3 and 5 /spl mu/m with the cutoff wavelength of 5.33 /spl mu/m. The maximum responsivity for 80-/spl mu/m diameter detectors was 1.00/spl times/10/sup 5/ V/W at 4.35 /spl mu/m while the detectivity was 3.41/spl times/10/sup 9/ cm Hz/sup 1/2//W. High-speed measurements were done at room temperature. An optical parametric oscillator was used to generate picosecond full-width at half-maximum pulses at 2.5 /spl mu/m with the pump at 780 nm. 30-/spl mu/m diameter photodetectors yielded 3-dB bandwidth of 8.5 GHz at 2.5 V bias.