6 November 1986 Analysis of InSb Photodiode Low Temperature Characteristics
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The quantum efficiencies of front and back illuminated indium antimonide photodiodes have been calculated with the aid of a computer model. This model describes the photodiode quantum efficiency, resistance, capacitance and responsivity for any given doping profile and temperature. The calculations show that front and back illuminated devices optimized for high resistance-area products at 77K have low quantum efficiencies when operated at 4.2K. These photodiodes are fabricated diffusion or ion implantation of a p-type layer in an n-type base with ~1 x 1015 cm-3 donors. The mechanism limiting the quantum efficiencies of these "normal" InSb photodiodes at low temperatures is reduced minority carrier diffusion lengths in the base layer. This effect is minimized by reducing the donor concentrations of the n-type base layer to ~ 1 x 1014 cm-3, thereby increasing the depletion layer width, carrier lifetimes and diffusion lengths of photogenerated minority carriers. High quantum efficiencies from 1-5 microns can then be achieved at 4.2K with front illuminated photodiodes provided that the p-type layer thickness < 2 microns. High quantum efficiencies may also be achieved at low temperature with back illuminated devices fabricated from high purity base layers as thick as ~10 microns provided that the surface recombination velocity < 102 cm/sec. or the base layer is depleted by reverse biasing the photodiode.
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Richard Schoolar, Richard Schoolar, Elizabeth Tenescu, Elizabeth Tenescu, } "Analysis of InSb Photodiode Low Temperature Characteristics", Proc. SPIE 0686, Infrared Detectors, Sensors, and Focal Plane Arrays, (6 November 1986); doi: 10.1117/12.936519; https://doi.org/10.1117/12.936519

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