Low frequency noise-dark current correlations in HgCdTe infrared photodetectors

Abstract

In this paper, low frequency noise and dark current correlation is investigated as a function of reverse bias and temperature for short-wave infrared (SWIR), mid-wave infrared (MWIR), and long-wave infrared (LWIR) HgCdTe homo-junction photodetectors. Modelling of dark current-voltage characteristics shows that the detectors have ohmic-behavior under small reverse bias, thus enabling further analysis of 1/f noise-current dependences with the empirical square-law relation (S_I ∼ I²) at different temperature regions. It is found that for the SWIR and MWIR devices, the total 1/f noise spectral density at arbitrary temperatures can be modelled by the sum of shunt and generation-recombination noise as <i>S</i>_I(<i>T</i>,<i>f</i>)=[<i>α</i>_{<i>S</i><i>H</i>}<i>I</i><i>S</i><i>H</i>2(<i>T</i>)+<i>α</i>_{<i>G</i>-<i>R</i>}<i>I</i><i>G</i>-<i>R</i>2(<i>T</i>)]/<i>f</i>, with no contribution from the diffusion component observed. On the other hand, for the LWIR device the diffusion component induced 1/f noise that cannot be overlooked in high temperature regions, and a 1/f noise-current correlation of <i>S</i>_I(<i>T</i>,<i>f</i>)={<i>α</i>_s[<i>I</i><i>D</i><i>I</i><i>F</i><i>F</i>2(<i>T</i>)+<i>I</i><i>G</i>-<i>R</i>2(<i>T</i>)]+<i>α</i>_{<i>S</i><i>H</i>}<i>I</i><i>S</i><i>H</i>2(<i>T</i>)}/<i>f</i> is proposed, with a shared noise coefficient of α_s ≅ 1 × 10^-9 which is close to that calculated for shunt noise. The 1/f noise-current correlation established in this work can provide a powerful tool to study the low frequency noise characteristics in HgCdTe-based photodetectors and to help optimizing the "true" detectivity of devices operating at low frequency regime.