Low-frequency noise limitations of InAsSb-, and HgCdTe-based infrared detectors

Abstract

The 1/f noise in midwavelength InAsSb- and HgCdTe-based unipolar barrier infrared detectors, grown on GaAs substrate, are studied both experimentally and theoretically. The examination of the dark current reveals three current components: leakage, diffusion, and generation-recombination. The first dominates in the low-temperature region for all devices, while diffusion and generation-recombination components dominate in the high-temperature region. For InAsSb-based detectors with cut-off wavelength 5.6 μm at 230 K, the measured 1/f noise can be exclusively attributed to the leakage current (which has the surface origin), which means that noise coefficients (relative noise) of generation-recombination and diffusion currents are small with respect to the leakage-current induced 1/f noise. In the HgCdTe-based barrier detector with cut-off wavelength 3.6 μm at 230 K, all current components induce measurable 1/f noise, but the leakage current is effectively suppressed, consequently, 1/f noise connected with generation-recombination and diffusion currents can be isolated. For this detector, the relative 1/f noise of generation-recombination and diffusion current decrease versus temperature with an exponential manner but the relations between 1/f noise coefficients, observed for InAsSb-based devices, hold true. Then, an important conclusion is that the improvement in the above sensors detectivity, for slow varying signals, can be achieved by reducing the leakage current which can be the source of 1/f noise even at room temperature, where the total current is dominated by the diffusion component.