Photosensitive Elements Research Articles

Calculation of parameters of image receivers on CCD structures while aircraft survey of the earth surface

The article provides an analysis of the noise characteristics of optoelectronic image receivers on matrix photosensitive CCD structures with tape addressing and their influence on the resolution of optical-electronic image sensors under low light conditions. The distinctive ability of the CCD at low levels of illumination is limited mainly by noise in the background charge and the noise of the process of capturing the carriers. Batch addressing matrices include FCCD with a time delay and accumulation (TDA), the use of which can dramatically increase the signal-to-noise ratio and, as a result, realize high sensitivity. One of the main advantages of matrices with TDA is the ability to hybridize them into superlines, the number of elements of which reaches tens of thousands. Modern matrices of TDA are built on the principle of partitioning. Each section of such a matrix makes it possible to carry the charge across the columns in the direction of the register. Since the sections are controlled independently (or partially independently), it is possible to regulate the number of accumulation lines, and consequently the sensitivity of the CCD of the TDA, by sequentially disabling them. Thus, the regulation of the sensitivity of the CCD is carried out and the dynamic range of the CCD and the observation system in general is expanded. To achieve this goal, a mathematical expression was obtained for calculating the number of lines of light sensory elements of a CCD, which should be used when surveying the earth's surface in conditions of low light. In this case, the number of elements along the length of the receiver is determined by the achievement of the required signal / noise ratio, in which the real resolution is determined by the minimum geometric dimensions of the photosensitive element.

Characteristics of vertically stacked graphene-layer infrared photodetectors

We evaluate the characteristics of the vertically stacked graphene-layer infrared photodetector (VS-GLIP). Each period of the stack (which constitutes the GLIP) consists of a GL (serving as a photosensitive element with a floating potential) sandwiched between barrier layers made of the van der Waals materials, and highly conducting emitter and collector contact n-GLs. The operation of VS-GLIPs is associated with the interband photoexcitation of electrons from the GLs (direct or followed by the tunneling), injection of the electrons from the emitter layer and the collection of both the photoexcited and injected electrons by the collector layer. At a small probability of the electron capture into the floating GLs, each GLIP section exhibits an elevated photoconductive gain. Due to the vertical multi-GLIP structure the absorption efficiency can be close to unity. Due to this and because the photocurrents produced by each GLIP in the stack are summarized, the VS-GLIP can exhibit elevated detector responsivity and detectivity, in particular, exceeding those of the GLIPs.

Investigation of CdHgTe-Based FPA Heterogeneity

The spatial heterogeneity of spectral responses to the focal plane arrays (FPA) photosensitivity of different photosensitive elements based on CdHgTe (cadmium–mercury–tellurium—CMT) solid solutions is studied. The investigation methodology for spectral responses of photosensitivity is described. The distribution of the photosensitivity long-wavelength limit for a 6 × 576 bar of photosensitive elements (PSE) is presented. The average composition and the CMT composition measurement error for all elements of the bar are calculated. The computed error comparison of the photosensitivity long-wavelength limit of selected PSE and of the value of limit in the PSE array local area are made. The efficiency of FPA quality control express-methodology is in respect to distribution uniformity of CMT composition on the array area.

Analysis of Photoelectric Characteristics of UV-Range Focal Plane Arrays

Photoelectric characteristics of the focal plane arrays working in the visual-blind UV spectral range are studied. The dependences of the signal-to-noise ratio (SNR) on the integration time and the bias voltage on photodiodes and I–V characteristics of the photodiodes are measured. It is shown that ROIC noise dominates over the noise of photosensitive elements. The results indicate that the maximum integration time and bias voltage are needed to reach the best SNR. The method used to measure the I–V characteristics after hybridization with ROIC makes it possible to measure the dark currents of the individual photodiodes at typical values of 4 × 10–15 A.

Real-Time Control of Nonflatness of Components of Infrared-Range Flip-Chip Photodetectors

A possibility of using the autocollimation and interference methods for real-time nondestructive check of the wafer nonflatness of photodetector arrays that are sensitive in the infrared range and are fabricated by the flip-chip technology is considered. These methods allow monitoring the wafer nonflatness and the maximum deflections. These methods are applied in the present study to measure the wafer nonflatness of fragments of silicon slices and arrays of photosensitive elements on GaAs substrates, as well as the wafer nonflatness of photodetectors at different stages of fracture and in the course of thermal cycling.

像素偏振成像系统的耦合实现

The coupling technology of the pixel polarization imaging system was studied by aligning the pixel polarizer array with the CCD photosensitive element. Aiming at the problem that the polarizer group array and CCD size do not match, a variety of process methods were used for processing, and a complete coupling alignment process was proposed. The imaging system developed in this paper can obtain four Stokes components with different polarization directions through one imaging detector. After operation and post-processing, it could also obtain the linear polarization image and the linear polarization angle image of the captured object, which realized the polarization enhancement of the image. The required polarization image facilitates the acquisition of target information in a complex environment.

ИНФРОКРАСНЫЕ ПРИЕМНИКИ ИНФОРМАЦИИ НА ОСНОВЕ ПОЛУПРОВОДНИКОВЫХ КОМПОЗИТНЫХ МАТЕРИАЛОВ

The article presents a phototransistor (PTSH - Schottky field-effect transistor) with a Schottky barrier based on an IrSi-Si contact and an p-channel type, which has a high photosensitivity and a more wider region of spectral sensitivity compared to Schottky diodes and MOS (metal oxide semiconductor) and MDS (metal-dielectric-semiconductor) structures. The current-voltage characteristics of breech-block of the field-effect transistor controlled by the Schottky barrier are investigated on the basis of the IrSı-Sı contact. The dependence of breech-block currents on the voltage is determined. Essential increasing of Schottky-matrixes filling coefficient is enriched by charge readout, stored in diode Schottky, not with help DCC (devices with charge coupling) – registers, but by its injection in to signal wire, by analogy with DCI (devices with charge injection) – to structures on narrow-band gap semiconductors. In this case multi element matrix contains horizontal wires for inquiry elements selected line, vertical signal wires, MOS-key (metal-oxide-semiconductor) for connection interrogated column and matrix of photosensitive elements, every of them consist of photosensitive diode Schottky and MOS-key. By it is an experimental method set that, dependence ofcurrent of breech-block of the field transistor of Schottkyshows with the induced channel, that for tension with theinfrared of transistor structure, the positive charge retained intape of IrSi runs down in silicic tape, forming a photoelectric inthe aim of breech-block. The considered infrared Sensor can be combined with the elements of the integrated circuits, that opens wide prospects for his use in multielement infrared photos receivers of large degree of integration.

结电容对不同光敏元尺寸InGaAs探测器I-V特性测试的影响

结电容对不同光敏元尺寸InGaAs探测器I-V特性测试的影响

Current–Voltage Characteristics of n-B-p Structures with Absorbing In0.53Ga0.47As Layer

A topical problem of photoelectronics is the development of array photodetector devices of the near infrared spectral range based on the InxGa1–xAs/InP epitaxial layers of the megapixel format. In this paper, we present the results of studies of current–voltage characteristics of photosensitive elements in arrays of the 320 × 256 format with a step of 30 μm based on heteroepitaxial structures with an InGaAs absorbing layer on InP short-wave infrared substrates. Arrays of photosensitive elements (PSEs) are fabricated using planar, mesa, and mesa planar technologies based on nB(Al0.48In0.52As)p-structures. In arrays produced using the mesa planar technology based on nB(Al0.48In0.52As)p-structures, small dark current and ampere–watt sensitivity to IR radiation of the 1–1.7 μm range are shown to combine successfully at low bias voltages. Electrophysical parameters of functional layers of initial heteroepitaxial n-B-p structures affect efficiently the dark currents and ampere–watt sensitivity of the array elements. Based on these studies, parameters of the n-B(Al0.48In0.52As) functional layers of p-structures were optimized and high-efficiency photodiode arrays of the 320 × 256 format with a step of 30 μm and structures of the 640 × 512 format with a step of 15 μm were fabricated with a defectiveness not exceeding 0.5%.

Rotating Mirror Digital Streak Camera for Investigation of Fast Processes

A TKPF269 rotating mirror digital streak camera with a photosensitive element based on a CMOS array was developed for the purpose of replacing film in high-speed streak cameras (SFR-2M, USF-2, etc.). A brief description of the TKPF269 streak camera design is given. The space-time picture of the emergence of light from the ends of optical fibers upon firing of an explosive in a model assembly was simultaneously recorded by a TKPF269 streak camera and an USF-2 streak camera to compare the metrological characteristics of these devices. The results of experimental data processing are presented.

Rotationally Tunable Two-Beam Interferometer with a Fixed Photosensitive Element. Part II. Interferometer Based on a Beam-Splitter Unit

Rotationally Tunable Two-Beam Interferometer with a Fixed Photosensitive Element. Part II. Interferometer Based on a Beam-Splitter Unit

Quantum-Chemical Investigation of Molecular Structure and Thermodynamic Properties of Spiropyran Molecules

Spiropyrans are heterocyclic organic compounds known for their photochromic properties which are of perspective use for technology. They can be potentially used as the elements of molecular machines, optical data recording, modulated light filters and numerous hybrid materials. The key characteristic of such compounds is an ability to enter a photochromic reaction, taking place upon irradiation with UV light (see Figures 1 and 2). To develop more compounds which can possibly be of practical use the most important problem is to investigate their chemical properties both theoretically and experimentally. To determine the optimal geometric structures for both spiro- and mesocyanine forms of 1,3,3,6’-tetramethyl-8’-formylsporoindoline-2,2’-[2H]-chromene-3 and 3,8’-dimethyl-6’formylspiro-(-4-oxo-3,4-dihydro-2H-1,3)-benzoxasine-2,2’-[2H]-chromene-7 (objects 1 and 2 respectively) using the DFT approach, calculations of quantum chemistry were used. All the computations were carried out in GAMESS software. In this research we used B3LYP, CAM-B3LYP, wB97, M11 and TPSSh functionals in conjunction with 6-311++G(d,p) basis set. In our studies we were able to compare experimental gas-phase IR spectra with the quantum-chemically computed one. This allowed us to consider the TPSSh functional as the best model for these compounds due to the most accurate geometrical structures and thermodynamic functions obtained with its use. In addition, it was possible to compute the photoinduced products of the isomerization reaction (see Figure) of our objects and their UV/Vis spectra which were also compared with the experimental spectra of thin films. Comparison allowed us to consider high accuracy of computed data. However, an attempt to find the optimal molecular structure for the cis-isomer of the second object was unsuccessful. Except for the B3LYP functional, none of the listed above could provide us with the reliable structure and, therefore, other properties. For this reason, it was only possible to compute the reliable reaction enthalpies for the one precursor molecule. The reaction enthalpies listed in the Table 1 are considered to be optimal for using such a compound as a photosensitive switch element because it is bigger than 10 kJ/mole but no more than 100 kJ/mole. From this it follows, that spontaneous switching probability is acceptably small, although at the same time such an amount of energy is practically feasible. Reaction ∆r H(298.15 K), kJ/mol156.392-11.783-68.17

Long-Wave Infrared Focal Plane Arrays Based on a Quantum-Well AlGaAs/GaAs Structure with 384 × 288 Elements

The characteristics of focal plane arrays (FPAs) based on (quantum-well infrared photodetector) QWIP structures with 384 × 288 elements spaced at the intervals 25 μm are investigated. The difference in spectral and current–voltage characteristics is established for epitaxial QWIP wafers. The output signal is found to vary over the area of photosensitive elements with gradients in different directions. The photoelectric FPA parameters depend strongly on the temperature of the cooled assembly and the bias at the photosensitive element. The noise-equivalent temperature difference is 30 mK at the frame rate 120 Hz and the cooled assembly temperature 65 K.

Precision Etching of Thin Doped Silicon Layers

The optimum etchant composition for precise removal of a thin high-doped silicon gettering layer is determined. It is found that the best-controlled etching is provided by the following composition: HNO3: HF: CH3COOH = 40: 1: 1. This composition etches the entire gettering layer away while preserving the required thickness of the contact layer, which prevents the space-charge region of the p–n junction from emerging at the back surface of the base of a photosensitive element. Thus, this etchant provides an opportunity to reduce the magnitude of dark currents and raise the percentage yield.

Optically functional isoxanthopterin crystals in the mirrored eyes of decapod crustaceans

The eyes of some aquatic animals form images through reflective optics. Shrimp, lobsters, crayfish, and prawns possess reflecting superposition compound eyes, composed of thousands of square-faceted eye units (ommatidia). Mirrors in the upper part of the eye (the distal mirror) reflect light collected from many ommatidia onto the photosensitive elements of the retina, the rhabdoms. A second reflector, the tapetum, underlying the retina, back-scatters dispersed light onto the rhabdoms. Using microCT and cryo-SEM imaging accompanied by in situ micro-X-ray diffraction and micro-Raman spectroscopy, we investigated the hierarchical organization and materials properties of the reflective systems at high resolution and under close-to-physiological conditions. We show that the distal mirror consists of three or four layers of plate-like nanocrystals. The tapetum is a diffuse reflector composed of hollow nanoparticles constructed from concentric lamellae of crystals. Isoxanthopterin, a pteridine analog of guanine, forms both the reflectors in the distal mirror and in the tapetum. The crystal structure of isoxanthopterin was determined from crystal-structure prediction calculations and verified by comparison with experimental X-ray diffraction. The extended hydrogen-bonded layers of the molecules result in an extremely high calculated refractive index in the H-bonded plane, n = 1.96, which makes isoxanthopterin crystals an ideal reflecting material. The crystal structure of isoxanthopterin, together with a detailed knowledge of the reflector superstructures, provide a rationalization of the reflective optics of the crustacean eye.

Optimization of the Parameters of PbSB-based Polycrystalline Photoresistors

Photosensitive elements based on polycrystalline lead sulfide layers are investigated. The influence of heterogeneous reactions at the crystallite–environment interfaces on the photosensitive-element characteristics is considered. It is shown that heat treatment in vacuum can be used to significantly change the parameters of the as-fabricated structures and optimize them for specific optoelectronic systems. A model is proposed to explain the nature of the observed phenomena.

OPTICAL FREQUENCY TRANSDUCER BASED ON DUAL-GATE MOSFET WITH AN ACTIVE INDUCTIVE ELEMENT

Background. A perspective trend in the development of optical radiation transducers is using of dependencies of reactive properties of semiconductor transistor structures with negative resistance on optical radiation effect and creation of frequency optical radiation transducers on the basis of these properties. Application of optical-frequency transformation enhances noisestability, accuracy and enables to expand a measuring range, to obtain outputs higher than amplitude ones and to improve metrological performances of the transducers. Using frequency as an informative parameter allows excluding the analog-to-digital transducers during information processing, and reducing the cost of monitoring and control systems. The principle of “optical powerfrequency” transformation can be implemented using semiconductor structure containing self-sustained oscillator and photoresistor as a photosensitive element. Active inductance resolves the problem of low quality factor inherent in the passive inductor. Furthermore, it overcomes compatibility issue of passive inductor's size with the integrated circuit's sizes and allowscompletely making transducer as an integrated circuit. So, it is necessary to construct a mathematical model of the optical frequency transducer to analyze its properties and to obtain the dependencies of active and reactive components of the impedance of the semiconductor structure, the equation of sensitivity and the transfer function.Objective. The aim of the paper is to determine the transfer function and equation of sensitivity for optical transducer with an active inductive element by solving Kirchhoff’s system of equations composed for equivalent circuit of the transducer.Methods. The determination of the transistor structure impedance was made by solving the Kirchhoff’s system of equations, composed for equivalent circuit of frequency optical transducer. The characteristics describing dependencies ofreactive and active components of the oscillator’s impedance on optical power were obtained by computer simulation using the MATLAB numerical computing environment.Results. The mathematical model for description of the properties of frequency optical transducer with an active inductive element was developed. The transform function and relative sensitivity analytical equations were estimated to describe the action of transducer. The values of relative sensitivity are equal to 2 – 11.5 kHz/ μWt/cm2. Accuracy of developed mathematical model is ±5%.Conclusions. The optical transducer with an active inductive element has a high sensitivity in the range of low values of optical power. It makes possible to measure even low optical signals. Proposed model describes the dependence of the impedance of the transistor structure – which is basic for the transducer – on power of optical radiation.Keywords: optical transducers; frequency transducers; negative resistance; photoresistor.

Космический тепловизионный мониторинг нефтегазопроводного транспорта

Oil and gas pipelines require systematic supervision and control in order to ensure their safe exploitation, even more so during spring/autumn/summer thawing, freezing and flooding seasons when soil deformation is at its highest. In the article, several ways of Earth’s surface space monitoring are considered. It’s pointed out that infrared sounding appears to be the most promising method of space monitoring the condition of main and production pipelines. It’s due to infrared sounding’s unique capability to detect pipeline’s construction flaws and breaches. However, thermal imaging systems are still in need of significant development, due to high noise and low image contrast levels. As of present time, there are no universally applicable filters, capable of detecting and suppressing all types and levels of noise. Further development in this sphere requires broadening of the arsenal of algorithmic processing facilities, which remains insufficient. The quality of thermal imaging depends on temperature distribution on the surface of the examined object as well as characteristics and parameters of thermal imaging systems themselves. The variety of parameters in photosensitive elements of photodetective device’s matrix leads to the appearance of so-called geometric noises in thermal imaging devices. Correction of geometrical noises in thermal imaging systems is one of the key problems. The approach to the solution of this problem is considered in the article.

Optimizing the parameters of a system consisting of a photosensitive IR element based on multilayer structures with quantum wells and a silicon photoelectric multiplexer

This paper discusses the design and process principles involved in optimizing the noise-equivalent temperature difference of photodetectors based on multilayer structures with quantum wells in wide ranges of the structural and process limitations of silicon multiplexers, CMOS-technology design norms, and the parameters of photosensitive elements for the long-wavelength IR spectral region.

Design and Calibration of Real-Time 3D Coordinate Measurement System Based on Multi-Angle Intersection and Cylindrical Imaging

This paper presents a high-resolution real-time 3D coordinate measurement system based on multi-angle intersection and cylindrical imaging. The measuring angle is detected by the linear camera equipped with cylindrical lenses, whose field of view is a 3D space rather than 2D plane. This camera has prominent advantages in precise coordinate measurement and dynamic position tracking due to the high resolution and outstanding frame rate of linear CCD. Each camera is a 1D angle measuring unit which confirms an angle thereby a plane passing through the light spot. With three cameras arrangement in front of the measurement field, the 3D coordinate of the light spot can be reconstructed by multi-angle intersection. An accurate and generic calibration method is introduced to calibrate this camera. The proposed calibration method is based on nonparametric ideas to find the mapping from incoming scene rays to photo-sensitive elements, and this method (black box calibration) is still effective even if the lens distortion is high and asymmetric. It is applicable to a central (single viewpoint) camera equipped with any lenses. The proposed calibration method is applied to the 3D coordinate measurement system. The coordinate measurement accuracy of the designed system is better than 0.49mm.