HgCdTe Research Articles

Performance Limits of III–V Barrier Detectors

Minority-carrier lifetimes and diffusion lengths have been deduced from a comparison of band structure simulations and experimental measurements on mid-wave infrared InAsSb XBn and long-wave infrared InAs/GaSb type II superlattice (T2SL) XBp barrier detectors with low diffusion-limited dark current close to mercury cadmium telluride Rule 07 and high quantum efficiency. For the XBn devices, a lifetime of 1.9 μs was observed with a corresponding diffusion length of 14.5 μm. In contrast, the T2SL exhibited a much shorter lifetime of 7.5 ns, but the diffusion length of ∼ 7 μm was long enough to ensure that almost 90% of the photocarriers are collected. The lifetime appears to be Auger limited in the case of n-type InAsSb, but for the p-type T2SL, Shockley–Read–Hall (SRH) traps appear to dominate. In the second case, possible scenarios for the dominance of SRH recombination are discussed to identify pathways for further performance optimization.

Laser-based long-wave-infrared hyperspectral imaging system for the standoff detection of trace surface chemicals

A trace chemical detector is described that combines external-cavity quantum cascade lasers and a mercury cadmium telluride camera to capture hyperspectral images of the diffuse reflectance from a target surface in the long-wave infrared. The system is able to generate individual hypercubes in <0.1 s. When raster scanning the laser beam over the target surface, areal coverage rates of >60 cm2 / s have been achieved. Results are presented for standoff distances ranging from 0.1 to 25 m. Hyperspectral images generated by the system are analyzed for spectral features that indicate the presence of trace surface contaminants. This approach has been found to be highly capable of detecting trace chemical residues on a wide variety of surfaces, and we present a collection of detection results to demonstrate the capabilities of this technology. Examples include the detection of 10 μg of saccharin powder on a wide range of substrates, 0.2 μg of an explosive residue on a computer keyboard, residual pharmaceuticals within a plastic baggie, and a contaminated fingerprint on cell phone case.

Characterization of mid-wavelength quantum infrared cameras using the photon transfer technique

Noise plays a fundamental role in connection with theoretical limits in the field of inverse thermal problems, since the solution accuracy for such inverse problems is decisively influenced by noise-induced errors in temperature measurements. There are eight standard assumptions proposed by Beck and Arnold (1977), Beck (1979), Beck et al. (1985) and Özisik and Orlande (1999) for the statistical description of measurement errors (noise) which should be fulfilled in order to adequately solve an inverse heat conduction problem. Therefore, it is of utmost importance for thermography measurements that the real infrared camera properties (and especially the noise performance) are well characterized and their influence on the measurement results is known and considered. Within the scope of this work three different mid-wavelength infrared cameras (based on indium antimonide and cadmium mercury telluride detectors) from various manufacturers were characterized with respect to the above mentioned prerequisites by means of the so called photon transfer technique. One of the results show that the tested IR quantum detectors are mostly photon-noise limited and therefore subject to a pronounced Poisson noise characteristic, i.e. the noise signal level (signal variance) depends on the signal intensity. This in turn violates one of the basic prerequisites of most inverse heat conduction approaches, which are relying on an additive noise model with constant variance. In addition, the camera gain constants for two camera models were determined using the photon transfer technique. They are 433 photons/DN or 281 photons/DN and are a measure of the sensitivity of the camera, i.e. the number of incident photons that result in a measurable signal change in the thermographic image.

Zero dark current in H2RG detectors: it is all multiplexer glow

We present the analysis of James Webb Space Telescope near-infrared H2RG detectors with a 5-μm cutoff, which shows that, at temperatures <60 K, there is no measurable dark current. Instead, the observed signal in dark exposures is almost entirely due to multiplexer glow that arises as each pixel is selected. We are able to separate the per-sample glow from the time-dependent dark current by comparing the observed signal in both continuous and sparsely sampled dark exposures. Such explicit tests are required to break the degeneracy between dark current and uniform amplifier glow. We show that the glow is lower within the regions of the detector that are missing the epoxy back fill (voids). We also find that the glow from each pixel extends out to a radius of several pixels. Because of the higher sampling frequency of subarray observations, the per-sample glow leads to a higher apparent dark current in subarray exposures. Finally, we show that the magnitude of the glow is affected by the pixel source follower current, the pixel clocking rate, and the number of outputs running in parallel. Our measurement of an insignificant dark current shows that the detector noise is no longer limited by the quality of the mercury cadmium telluride layer but instead by the multiplexer and readout electronics.

Near-field negative electroluminescent cooling via nanoparticle doping

Modulating the photon tunneling probability is the key to control the near-field radiative heat transfer (NFRHT) between two objects. It has been found that nanoparticle doping technology can enable plentiful resonance modes which significantly adjust photon emission spectra. In this work, we theoretically analyze the performance of a near-field negative electroluminescent refrigeration (NFNELR) system consisting a Mie-metamaterial emitter and mercury cadmium telluride (MCT) receiver with spacing between them less than the thermal wavelength. The emitter consists of graphene/SiC core-shell (GSCS) nanoparticle-embedded thin film of Si deposited on bulk Si. We show that with the inclusion of GSCS nanoparticles, the thin layer of Mie-metamaterial acts like an effective medium that excites radiative heat transfer for the photons above the band gap of MCT. We analyze NFNELR performance for various bias voltages, various cryogenic temperatures, various volume fractions and various chemical potentials of GSCS nanoparticles. We also would like to emphasize that in order to improve the performance of the NFNELR system, the host matrix materials chosen are not necessarily stationary. These results provide a powerful way to rouse and regulate the NFRHT, meanwhile in turn, open up a way to explore actual development and present some guidance for optimal design of NFRHT.

High-Q diamond microresonators in the long-wave infrared.

High quality factor (Q) photonic devices in the room temperature thermal infrared region, corresponding to deeper long-wave infrared with wavelengths beyond 9 microns, have been demonstrated for the first time. Whispering gallery mode diamond microresonators were fabricated using single crystal diamond substrates and oxygen-based inductively coupled plasma (ICP) reactive ion etching (RIE) at high angles. The spectral characteristics of the devices were probed at room temperature using a tunable quantum cascade laser that was free space-coupled into the resonators. Light was extracted via an arsenic selenide (As2Se3) chalcogenide infrared fiber and directed to a cryogenically cooled mercury cadmium telluride (HgCdTe) detector. The quality factors were tested in multiple microresonators across a wide spectral range from 9 to 9.7 microns with similar performance. One example resonance (of many comparables) was found to reach 3648 at 9.601 µm. Fourier analysis of the many resonances of each device showed free spectral ranges slightly greater than 40 GHz, matching theoretical expectations for the microresonator diameter and the overlap of the whispering gallery mode with the diamond.

Imaging Infrared Spectrometer onboard Chandrayaan-2 Orbiter

Imaging Infrared Spectrometer (IIRS) is an imaging hyperspectral instrument for mineralogy of the lunar surface (including the hydroxyl signature). IIRS operates in the 0.8–5 μm spectral range with about 250 contiguous bands. It has 80 m ground sampling distance and 20 km swath at nadir from 100 km orbit altitude. Optical design is based on fore-optics and Offner (convex multi-blazed grating)-type spectrometer. Focal plane array is HgCdTe (mercury–cadmium–telluride)- based actively cooled to 90 K, having 500 × 256 pixels format with 30 μm pixel size. Electronics comprises proximity, logic and control, power supply and cooler drive electronics. Mechanical system is realized to house various subsystems, namely optics, detector, electronics and thermal components meeting the structural, opto-mechanical thermal component and alignment requirements. Thermal system is designed such that the instrument is cooled and maintained at fixed temperature to reduce and control instrument background. Aluminum-based mirror, grating and housing are developed to maintain structural as well as opto-mechanical and thermal requirements. This article presents IIRS realization and spectroradoimetric performance.

Effect of HgCdTe native oxide on the electro-physical properties of metal–insulator–semiconductor structures with atomic layer deposited Al2O3

Metal–insulator–semiconductor structures with atomic layer deposited (ALD) Al2O3 and ultra-thin native oxide were formed on n-type variband Hg1–xCdxTe of two different volume compositions x, referred to as MWIR and LWIR. It is shown that presence of native oxide prior to plasma-enchanced ALD process and origination of this oxide are crucial to properties of an insulator–semiconductor interface. Ultra-thin native oxide formed in glow discharge or remote RF plasma is much more stable than oxide formed during storage of sample in air and provides significantly improved interface quality. The positive sign of fixed charge introduced by plasma oxide is more preferable for an n-type semiconductor than the negative one, but obtained density of fixed charge up to 1 × 1012 cm−2 is still quite high and should be reduced. Density of slow surface states, being responsible for hysteresis of C–V characteristics, is much lower in case of plasma oxide, with C–V curves showing near-ideal high-frequency behavior.

Photodiodes based on p-on-n junctions formed in MBE-grown n-type MCT absorber layers for the spectral region 8 to 11 μm

Results of measurement of the dark currents and photocurrents of p-on-n photodiodes (PD) formed in In-doped MBE-grown n-type mercury cadmium telluride (MCT) films are reported. We used 3 in. in diameter (0 1 3) GaAs and (0 1 3) Si substrates. The p-on-n junctions were fabricated using the implantation of As+ ions followed by the thermal annealing activation. It was shown that the regime of background-limited performance (BLIP) of the p-on-n PD with experimentally measured long-wave cutoff wavelength (LW) cutoff (λc) of 11.1 and 10.3 μm at 77 K is observed up to elevated temperatures of 105 K and 117 K, respectively. The temperature dependence of the noise equivalent temperature difference (NETD) for p-on-n PD sized 30 × 30 μm was calculated taking into account only PD shot noise. It was shown that such LW p-on-n photodiodes allows to increase the operating temperature of IR FPA detectors up to 100–105 K with the NETD less than 30 mK.

Photoluminescence in Mercury Cadmium Telluride – a Historical Perspective. Part I: 1966-1996

This work presents a historical perspective on the studies of photoluminescence in mercury cadmium telluride (HgCdTe), one of the most important materials of infrared photoelectronics. The first part of the review considers the results of the studies performed during the early years of the development of the technology of this material (1966-1996). These studies were carried out mostly using samples of bulk crystals and epitaxial films grown by liquid-phase epitaxy. The results of the studies allowed for identification of the nature of optical transitions in HgCdTe, including excitonic emission, interband recombination, donor-acceptor pair recombination and recombination via shallow and deep levels, which greatly helped in maturing the material technology.

Адмиттанс барьерных структур на основе теллурида кадмия - ртути

Адмиттанс барьерных структур на основе теллурида кадмия - ртути

Comparative studies on the electronic transport in magnetically quantized low band gap semiconductor system

The Q1D system formed by magnetically confined system is attracting attention of researchers in device application because it is capable of over-looking the various techniques of fabrication difficulties and defects created by such fabrication techniques. In the presence of a high magnetic field, the transverse component of the energy dispersion relation gets quantized into various equally spaced energy levels called Landau levels and the motion of the carriers is completely restricted. However, the longitudinal component along the field is still free to move. The mobility of such system is enhanced when a low effective mass semiconductors n-HgCdTe (Mercury Cadmium Telluride) is used. The band structure of n-HgCdTe is found to be nonparabolic due to its low band gap according to Kane [Phadke and Sharma, 1975]. Recent publications, based on experimental verifications of transport coefficient of n-HgCdTe of Chen and Sher [Chen and Sher, 1982] show that the band structure of Mercury Cadmium Telluride (MCT) is more hyperbolic in nature rather than nonparabolic. The author has compared the effect of band structures on the various transport properties of MCT such as mobility, Seebeck coefficient, thermal conductivity, figure of merit (Z) etc. The figure of merit is a very important property of a material to be used in thermoelectric devices, such as cooler, refrigerator etc. The product of Z and temperature i.e. (ZT), a dimensionless quantity is found to be maximum for parabolic band structure and is followed by nonparabolic and hyperbolic band structures for all ranges of variation of temperature as well as magnetic field. Taking the hyperbolic band structure of MCT, the effect of high and low temperature scattering mechanisms on ZT is also observed.&#x0D; BIBECHANA 17 (2020) 34-41

Open Path Measurement of Atmospheric Transmission Spectra in the Region of 3000–3450 nm Using Tunable Mid Infrared Lidar

This paper reports the open path measurement of atmospheric transmission in the spectral region of 3000–3450 nm using a mid infrared tunable lidar in New Delhi (28.7oN, 77.1oE), India. Results on the measurement of atmospheric transmission in New Delhi are reported for the first time, to the best of our knowledge. A tunable infrared lidar system has been developed in-house, which transmits laser radiation with the wavelength interval of 1 nm in the above spectral band into the atmosphere. A 200-mm-diameter Cassegrain receiver telescope with mercury cadmium telluride (MCT) detector is used to collect the backscattered radiation from the atmosphere. The reflected laser radiation received from the tower located at a distance of 400 m is used to generate the transmission spectrum. Data recorded during the daytime measurements have been considered in this paper. Transmission spectra measured over several days showed a similar pattern, which confirmed the repeatability of the system performance. The measured spectra are also compared with the SkyCalc transmission model generated using the online database. Preliminary analysis indicated that these spectra had good agreement in general with a small shift in wavelength region. We have also analyzed the HITRAN database line-by-line and identified the possible major absorbing molecules in this band. The sources of air pollutants that absorb in this band and also discussed.

Возможности характеризации кристаллических параметров структур Cd-=SUB=-x-=/SUB=-Hg-=SUB=-1-x-=/SUB=-Te на подложке из GaAs методом генерации на отражение второй гармоники зондирующего излучения

Abstract Comparative results of computational simulation and experiment are provided, concerning the azimuthal angle dependency of the registered signal second harmonic reflected from CdxHg1–xTe structures and GaAs substrates at the normal incidence of probing laser radiation and azimuthal rotation of its polarization plane. The study of (013) GaAs substrate and buffer layers of CdTe|ZnTe|GaAs has revealed that the deviations from the (013) surface orientation with regard to crystal physics angles ϴ and φ are ~1–3° for GaAs substrates and up to 8° for buffer layers of CdTe|ZnTe|GaAs, while the amplitude of the signal second harmonic reflected from buffer layers can well be considered as inversely related to the full width of X-ray rocking curves at half-maximum. Experimental data show that the values of non-linear susceptibility tensor components for CdxHg1–xTe crystalline structure significantly exceed those for CdTe and GaAs.

MCT APD Detection System for Atmospheric Profiling Applications Using Two-Micron Lidar

An advanced detection system, based on mercury cadmium telluride avalanche photodiodes array, was implemented within a 2-μm lidar. Detection system characterization was conducted for performance evaluation including settling time, noise-equivalent-power (NEP) and dynamic range. Results indicated an average NEP of 1.4 fW/Hz1/2 per pixel. Lidar range resolved profiling demonstrated the dynamic range capability by measuring near-field aerosol scattering and far-field clouds reflection simultaneously.

HgCdTe Quantum Dot Over Interdigitated Electrode for Mid-Wave Infrared Photon Detection and Its Noise Characterization

In this paper, we report the development of mid-wave infrared (MWIR) photon sensor using solution-processed mercury cadmium telluride (Hg[Formula: see text]CdxTe) semiconductor colloidal quantum dots (CQDs) coated over interdigitated metallic electrode structure, having significant response in the MWIR spectral band range ([Formula: see text]–5.0[Formula: see text][Formula: see text]m) at room temperature. HgCdTe CQD has been chemically synthesized. We have characterized the optical and [Formula: see text] noise performances of the developed sensor to understand its behaviors at different operating biases as an introductory step toward development of large-format MWIR focal-plane arrays having similar pixel structure. The optimum biasing conditions have been experimentally evaluated at room temperature. We have achieved a noise equivalent power (NEP) of 2.5[Formula: see text]pW at 1.5-V bias voltage which corresponds to detectivity ([Formula: see text]) in the order of 108. This work highlights the development of low-cost colloidal HgCdTe quantum dot photodetectors and their utility in the monolithic infrared focal-plane arrays.

Gate Capacitance in Quantum Metal-Oxide-Semiconductor Field-Effect Transistor Devices of Technologically Important Materials

The Heisenberg's scientific theory of quantum science since its beginning has been proved to be instrumental in unlocking varied vital quantum phenomena. In what follows the Heisenberg's scientific theory has been used to derive the expressions for the gate capacitance in Quantum MOSFET Devices manufactured from completely different technologically vital nonstandard materials by formulating the 2D electron statistics under very low temperature so that the Fermi function tends to unity. For numerical computations we take Cd3As2, the best quality very high mobility semiconductor and non-linear optical (e.g., CdGeAs2) compounds from which quantum MOSFET devices are made of by using all types of anisotropies of band structures in addition to splitting of bands due to large fields of the crystals inside the frame work of Kane's matrix methodology that successively generates new two dimensional electron energy versus wave vector relation for both low and very large externally applied electric field of force respectively. Under many special conditions, the corresponding statistics and therefore the gate capacitance for the quantum MOSFETs, whose e–ks equation (e is carrier energy and ks is the 2D wave vector) are defined by various models of III–V semiconducting samples originally derived by Kane create special cases of our extended formalism. It's been found taking quantum MOSFETs of CdGeAs2, InAs, InSb, Hg1–xCdxTe and In1–xGaxAs yP1–y lattice matched to InP that the gate capacitance at the electrical quantum limit will exhibit monotonic increasing function with changing field at the surface, the applied voltage at the gate for each of the compounds and therefore the actual results have one to one correspondence with the energy band constants showing an inclination of asymptotic results at comparatively large values of the independent variables for all the cases. The gradient rates for all curves change from one material to a different material. With decreasing alloy composition, the gate capacitance will increase for each of quantum confined MOSFETs made of various alloy compounds. For the aim of coherent presentation we've got conjointly planned the periodical Fermi energy at high field of force limits and gate voltage for few quantum confined MOSFETs.

A Calculation Method for Response Spectrum of Mercury Cadmium Telluride Infrared Focal Plane Arrays Detector

The invention discloses a calculation method for a response spectrum of a mercury cadmium telluride infrared focal plane detector, and the method mainly comprises the propagation of incident light in the mercury cadmium telluride infrared focal plane detector, the transportation of carriers in a mercury cadmium telluride absorption layer, and the comprehensive design of the surface state composite model of the mercury cadmium telluride absorption layer and the response spectrum. The designed response spectral curve is consistent with the actual test results in the interference fringes and the decrease in quantum efficiency in the short-wave infrared region. This design method is of great significance for the response spectrum optimization of the mercury cadmium telluride infrared focal plane detector.

Synthesis and Fundamental Studies of Si-Compatible (Si)GeSn and GeSn Mid-IR Systems with Ultrahigh Sn Contents

A unique class of crystalline Ge1–ySny alloys with ultrahigh Sn concentrations reaching 33% as well as Si-doped analogues have been synthesized directly on large-area Si wafers by chemical vapor deposition (CVD). The band gaps of these materials are measured to be as low as 0.15 eV, which allows them to cover a significant portion of the coveted mid-IR optical range past 8 μm, making them a potential alternative to Hg1–xCdxTe for long-wavelength applications. The film synthesis, based on stoichiometric CVD reactions of polygermanes and stannanes, is carried out at temperatures between 240 and 290 °C, indicating that the alloys are stable at typical device-operating temperatures and at complementary metal oxide semiconductor-compatible conditions. The main difference between Ge1–ySny (y ≈ 0.33) and the more diluted alloys (y < ∼0.2) featured in prior studies is the predicted presence of a significant fraction of Sn–Sn bonds, which could have a profound impact on the structural and electronic properties in view of the large size mismatch between Ge and Sn. However, X-ray measurements of the lattice parameter over the entire 0–33% Sn compositional range show a linear dependence of the cubic lattice parameter consistent with Vegard’s law. Theoretical ab initio simulations assuming random alloys show a monotonic compositional dependence of the alloy energy of formation and confirm the experimental lattice parameter. The crystalline structure and the interface defects that accommodate the large lattice mismatch with the substrate are elucidated using transmission electron microscopy studies. Optical studies indicate that the fundamental direct band gap and other critical point features in the electronic structure also display a smooth compositional dependence, which should facilitate device engineering based on these materials.

Gold plasmonic material for enhanced Hg1–xCdxTe infrared absorption

There are potential applications for high operating temperature (HOT) Hg1-xCdxTe (MCT) infrared (IR) devices for both defense and commercial applications. MCT absorption can be raised either by increasing the absorber thickness or by lowering the operating temperature. However, if we can increase MCT absorption by using plasmonic materials, it will help in both HOT operation and increasing signal to noise ratio. We studied three Gold (Au) plasmonic structures for the absorption enhancement of MCT materials in the wavelength band of 3-7 μm. By using RF module in COMSOL multiphysics software, we found a large increase (1.85X) of MCT absorption when the optimized Au plasmonic structure is used. The increase in absorption at 4.5-6 μm is higher than that at 3-4 μm. The increased absorption due to plasmonic structure allows absorber thickness to decrease which leads to decrease in dark current and HOT devices. We report here record 90% increase in absorption of MCT material at room temperature at peak wavelength around 3.4 μm by using optimized plasmonic structure.