Noise characteristics of InAs/GaSb superlattice infrared photodiodes
A sophisticated noise measurement setup employing a switching unit to measure statistically relevant numbers of InAs/GaSb superlattice photodiodes has been developed. The noise current resolution limit of 20 fA Hz(-1/2) enables the characterization of focal plane array-sized InAs/GaSb superlattice homojunction photodiodes for the long-wavelength infrared at 77 K. To resolve midwavelength infrared photodiodes a junction area of about (400 µm)2 is required. Without switching unit and by using a dedicated low noise amplifier, noise currents down to 2 fA Hz(-1/2) can be achieved, allowing the noise characterization of mid-wavelength photodiodes with smaller junction areas. With this setup longwavelength and mid-wavelength InAs/GaSb superlattice photodiodes, with generation-recombination limited dark current behavior, are investigated at 77 K. The measured diode noise follows the theoretically predicted shot noise level within the white noise part of the spectra.