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Today, one of the main challenges in the quantum infrared detection field is to increase the operating temperature in order to reduce size, weight and power-cost (SWAP). However, this leads to two major issues: an increase in the number of random telegraph signal (RTS) pixels and a residual fixed pattern noise (RFPN) instability. To identify these noise sources and assess the performance of a component, numerous measurements at the operating temperature are necessary, which can be laborious. Nevertheless, there exists a noise quality indicator for detectors at high temperatures known as the Tobin factor. In this paper, our objective is to investigate and understand the relationship between random telegraph signal (RTS) pixels and the Tobin factor. The aim of this study is to evaluate the relevance of the Tobin factor extracted at high temperatures to forecast noise performance at operating temperatures. [ABSTRACT FROM AUTHOR]

Improving material quality is an essential step to maintain high electro-optical performance at higher operating temperature (HOT) of cooled II-VI infrared (IR) detectors. Indeed, the electrical activity of crystal defects affects their image quality and stability. A first investigation is to correlate the point defect populations with the crystal quality of the Cd1−xZnxTe (CZT) substrate, used for the growth of the Hg1−xCdxTe (MCT) active layer. For this purpose, spectrally resolved cathodoluminescence (CL) measurements were performed for wafers with low and high crystal quality, with a respective dislocation density of 1.8 × 104 cm−2 and 6 × 103 cm−2. At 295 K, both wafers showed band-to-band transition, and CL spectra were modeled with the generalized Planck law. However, at 10 K, CL spectra showed that the visibility of phonon replicas of the donor–acceptor pair (DAP ) transition at 1.57 eV is dependent on the crystalline order. In addition, the luminescence of the A-center defect ( V Cd - D ) was observed at 1.43 eV only in the low-quality CZT substrate. [ABSTRACT FROM AUTHOR]

Infrared cooled photodetectors must operate at higher temperatures to reduce their size, weight and power consumption (SWaP context). Their stability and image quality are then challenged by extra electrical activity of crystal defects. Knowledge of defect populations is mandatory to improve the material quality of the epitaxial Hg1−xCdxTe (MCT) active layer and the Cd1−xZnxTe (CZT) substrate. Positron annihilation spectroscopy with a slow positron beam was used to study near-surface open-volume defects profiles. Low- and high-momentum fractions (S , W ) were used to characterize the Doppler broadening of the 511 keV electron-positron pair annihilation-line as a function of the positron implantation energy E . The results show that three regions can be identified beneath the surface of the as-grown non-optimized MCT layer. The quasi-linear relationship between the annihilation characteristics in the regions suggests that the defect populations mainly correspond to the same open-volume defect in different concentrations. The probed defect is thought to be related to the mercury vacancy. This hypothesis is discussed in an original way with near-surface elemental profiles using scanning transmission electron spectroscopy combined to energy dispersive x-ray spectroscopy (STEM-EDX). Afterwards, this approach is extended to CZT substrates showing that surface and bulk properties of those fabricated by LYNRED tend to match those that are state-of-the-art. A common open-volume defect is probed, in concentration estimated by Hall effect around 1015 cm−3 and thought to be related to the cadmium vacancy. [ABSTRACT FROM AUTHOR]

An automated random telegraph signal (RTS) detection and characterization method and a blinking noise and slow drift separation method adapted to focal-plane arrays have been developed and applied to study the evolution of the number of RTS pixels and the amplitude of the blinking signal as functions of the reverse bias voltage and temperature. The results show that the physical characteristics of the RTS follow Arrhenius laws and increase with bias. The origin of this increase in the amplitude as a function of the reverse bias is discussed. [ABSTRACT FROM AUTHOR]

Random telegraph signal (RTS) noise is present in all bands of the infrared spectrum from λ = 2.5 μm (short-wavelength infrared) to λ = 15.75 μm (very long-wavelength infrared) and decreases the performance of infrared photodetectors. The main features of RTS noise such as the jump amplitude and RTS frequency are defined, and their dependence as a function of focal-plane array (FPA) temperature was measured for all bands of the infrared spectrum. Both of these features comply with a Boltzmann activation law $$ \left( { \propto {\hbox{e}}^{{\frac{{ - E_{\rm{a}} }}{k_{\rm B} T}}} } \right) $$ , and their activation energies scale with the bandgap. Comparison of three different HgCdTe mid-wavelength infrared photodetector technologies was also performed, showing that the optimized n-on- p improvement of operability (AOP) and p-on- n high-operating-temperature technologies show a reduced number of pixels exhibiting RTS noise (by about two decades) in comparison with standard n-on- p technology. [ABSTRACT FROM AUTHOR]

At high temperature, infra-red focal plane arrays are limited by their performance in operability, detectivity D or noise equivalent temperature difference. Trap characterization and defect studies are necessary to better understand these limitations at high temperature. In this paper, we use deep level transient spectroscopy to study electrically active defects in mercury cadmium telluride n/ p diodes. The material investigated has a cut-off frequency ( λ) of 2.5 μm at 180 K and p doping performed with mercury vacancy. Trap energy signatures as well as capture cross-section measurements are detailed. A low temperature hole trap close to midgap is observed in the range 150-200 K with an activation energy around 0.18 ± 0.025 eV. A high temperature hole trap is also observed in the range 240-300 K with an activation energy of 0.68 ± 0.06 eV. A hole capture cross-section of 10 cm is obtained for both traps. The nature of the defects and their correlation with dark current are discussed. [ABSTRACT FROM AUTHOR]