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14 May 2007 1/f noise in HgCdTe infrared gated photodiodes
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In this work gated midwave infrared (MWIR) Hg1-xCdxTe photodiodes are used to investigate the physical origin of 1/f noise generation. Gated photodiodes were fabricated on liquid phase epitaxy p-type HgCdTe MWIR material with a vacancy doped concentration of 1.6 x 1016cm-3 and x = 0.31. CdTe was thermally deposited and used as both a passivant for the HgCdTe and a mask for the plasma-based type conversion, and ZnS was used as an insulator. Fabricated devices show a R0A of 1-5x104&OHgr;cm2 at 77K with zero gate bias. Application of 2V to the gate improves the R0A by more than two orders of magnitude to 6.0 x 106&OHgr;cm2, which corresponds to the p-type surface being at transition between depletion and weak inversion. Trap-assisted tunelling (TAT) current was observed at negative gate biases and reverse junction biases. For gate biases greater than 3V a field-induced junction breakdown was observed. Gated photodiodes show diffusion limited behaviour at zero bias above 200K, and TAT, band-to-band tunnelling, and generation-recombination (GR) limited behaviour below, for gate biases from -8V to 8V. Field-induced junction breakdown current was also observed to be temperature independent. Noise current, In = &agr;I&bgr;f-0.5 trend was observed above 200pA reverse bias dark current, with &agr; = 3.5 x 10-5 and &bgr; = 0.82, which corresponds to the TAT dominated region. Below 200pA, junction GR current starts to dominate and this previously mentioned trend for In is no longer observed. Junction GR current was not seen to be correlated with 1/f noise in these photodiodes.
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R. J. Westerhout, C. A. Musca, J. Antoszewski, J. M. Dell, and L. Faraone "1/f noise in HgCdTe infrared gated photodiodes", Proc. SPIE 6542, Infrared Technology and Applications XXXIII, 65420E (14 May 2007);

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