Surface leakage current in 12.5 mm long wavelength HgCdTe infrared photodiode arrays.
Long wavelength (especially >12 mm) focal plane array (FPA) infrared detection is the cutting edge technique for third generation infrared remote sensing. However, dark currents, which are very sensitive to the growth of small Cd composition HgCdTe, strongly limits the performance of long wavelength HgCdTe photodiode arrays in FPAs. In this Letter, 12.5 mm long wavelength Hg1 xCdxTe (x0.219) infrared photodiode arrays are reported. The variable area and variable temperature electrical characteristics of the long wavelength infrared photodiodes are measured. The characteristics of the extracted zero bias resistance area product (l/R0A) varying with the perimeter to area (P/A) ratio clearly show that surface leakage current mechanisms severely limit the overall device performance. A sophisticated model has been developed for investigating the leakage current mechanism in the photodiodes. Modeling of temperature dependent I V characteristic indicates that the trap assisted tunneling effect dominates the dark current at 50 K resulting in nonuniformities in the arrays. The extracted trap density, approximately 1013 1014 cm 3, with an ionized energy of 30 meV is determined by simulation. The work described in this Letter provides the basic mechanisms for a better understanding of the leakage current mechanism for long wavelength >12 mm) HgCdTe infrared photodiode arrays.
Optics letters