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Matrix photosensitive elements based on a HgCdTe semiconductor solid solution on silicon substrates with 640 × 512 elements at a pitch of 25 μm with a long-wavelength sensitivity of 5 μm at half maximum are designed and produced. The scheme and topology are developed according to which matrix multiplexers with 640 × 512 elements at a pitch of 25 μm, which ensure operating modes at a clock frequency up to 10 MHz, are manufactured. Using a hybrid assembly method on indium bumps, a matrix photodetector with 640 × 512 elements at a pitch of 25 μm is produced. The best photodetector specimens are characterized by the following parameters: average NETD value 99.5%.

Low-temperature magnetotransport in a quasi-two-dimensional electron system based on a selectively doped GaAs quantum well with two occupied quantum-confinement subbands with one-dimensional periodic modulation of a potential is investigated. It is shown that commensurability oscillations of the resistance in this electron system coexist with magneto-intersubband oscillations. It is found that, in addition to commen-surability oscillations, the one-dimensional periodic potential in the two-subband electron system leads to the modulation of the magneto-intersubband oscillation amplitude. The experimental results are explained by the formation of Landau bands in the quasi-two-dimensional electron system with one-dimensional periodic modulation of the potential.

The effect of microwave radiation on low-temperature electron magnetotransport in a square antidot lattice with a period of d = 0.8 micrometer based on a GaAs quantum well with two occupied energy subbands E1 and E2 is investigated. It is shown that, owing to a significant difference between the electron densities in the subbands, commensurability oscillations of the resistance in the investigated antidot lattice are observed only for the first subband. It is found that microwave irradiation under the cyclotron resonance condition results in the formation of resistance oscillations periodic in the inverse magnetic field in the region of the main commensurability peak. It is established that the period of these oscillations corresponds to the period of magneto-intersubband oscillations. The observed effect is explained by the increase in the rate of intersubband scattering caused by the difference between the electron heating in the subbands E1 and E2., 5 pages, 4 figures

Electron transport in single GaAs quantum wells of widths from 22 to 46 nm with two populated quantum-confinement subbands ES and EAS is investigated at a temperature of T = 4.2 K in tilted magnetic fields B 72° and α > 85°, respectively. The origin of this unexpected behavior of magnetointersubband oscillations in tilted magnetic fields is discussed.

Growth-related structural defects present on the surface of InAlAs layers grown by molecular beam epitaxy on InP(001) substrates influence the temperature dependences of the current–voltage characteristics of Au/Ti/InAlAs Schottky barriers. It is established that these defects in the form of pits cause the appearance of regions with reduced barrier height. At a surface density of ≥107 cm–2, these defects significantly influence the parameters of the Schottky barriers at temperatures below 200 K.

This paper describes the design of readout integrated circuits (ROICs) for hybrid infrared focal plane arrays (IR FPAs). This work contains the estimation of the noise equivalent temperature difference (NETD) of IR FPAs based on frame and row integration of pixel signals in the spectral ranges of 8 to 14 and 3 to 5 μm. This paper also describes the development of ROICs for IR FPAs created with the use of mercury—cadmium—telluride (MCT) photodiodes and quantum well infrared photodetectors (QWIPs). The designed ROICs ensure the use of matrix and linear photodetector chips, including those with increased dark currents, in order to produce IR FPAs with temperature resolution corresponding to the world level of array analogs.

This paper presents the physical and technical principles of readout integrated circuit (ROIC) for reading and preprocessing focal plane array signals in the infrared spectral range 8–14 μm. The noise equivalent temperature difference of long-wavelength infrared focal plane arrays based on ROIC with frame integration of signals of multilayer quantum well structures is evaluated. The influence of technological limitations in silicon readout circuits for photo signals on the performance of IR focal plane arrays is analyze for a wide range of parameters of QWIP -based focal plane arrays and CMOS technology design rules.

Nonlinear magnetotransport of two-dimensional electrons in square antidot lattices prepared on the basis of selectively doped GaAs/AlAs heterostructures with the period that is much less than the electron mean free path in the initial GaAs quantum wells but is much larger than their Fermi wavelength has been studied. It has been shown that the character of the nonlinear transport of the two-dimensional electrons in the lateral lattices under study changes from classical to quantum with the decrease in the antidot radius. It has been found that the quantum lifetime increases in the magnetic field corresponding to the condition of equality of the cyclotron diameter of two-dimensional electrons and the antidot lattice period.

The absorption of terahertz radiation by a thin metal absorber in the bolometers of five different designs is analyzed. Main attention is paid to bolometers of three basic configurations: (i) conventional bolometers with a double-layer main optical cavity, (ii) conventional bolometers with an additional optical cavity, and (iii) inverted bolometers with an additional optical cavity. Analytical expressions that allow calculating the absorption spectra in all the considered bolometers are obtained. It is shown that conventional bolometers only with the main optical cavity made up of two dielectric layers, as well as conventional and inverted bolometers with both main and additional optical cavities, can have the absorptance close to unity in the terahertz range. At the same time, conventional terahertz bolometers are mainly selective, whereas inverted ones are broadband.

This paper gives the parameters of 320 × 256 element long-wavelength infrared photodetectors fabricated by a new improved technology based on heteroepitaxial mercury-cadmium-tellur structures. In these photodetectors, the variation of the photodiode bias voltage over the area of the array is minimized; inefficient photodiode regions related to both hybridization and spike-shaped growth defects of epitaxial films are eliminated; the current-voltage characteristics of the diodes in the resulting photodetectors are homogeneous and are limited by the diffusion current component up to −400 mV. The dark current is 0.25–0.45 nA, and R 0 A = (0.6–3) · 102 Ω · cm2. The voltage sensitivity, the threshold irradiance, and the average NETD at the maximum sensitivity are 11.8 · 108 V/W, 3.7 · 10−8 W/cm2, and 26.8 mK, respectively. The percentage of defective elements is 1.5%.

The architecture of silicon multiplexers for multielement IR photodetectors is considered. A review is given of industrially oriented developments of linear (1 × 32, 1 × 288, 1 × 576) and matrix (32 × 32, 128 × 128, 160 × 128, 320 × 256) silicon multiplexers for mid- and far-IR photodetectors based on cadmium-mercury-tellurium, lead-tin-tellurium, and multilayer structures with quantum wells. An analysis is made of the temperature resolution of matrix IR photodetectors based on multiplexers with row and frame integration of photo signals using micrometer to deep submicron CMOS technologies. Typical parameters of the multiplexer and some of the infrared photodetectors designed at the Rzhanov Institute of Semiconductor Physics, SB RAS are given.

The mechanism of occurrence of sensitivity of microbolometer detector arrays based on vanadium oxide to terahertz radiation are analyzed. Experimental data are given showing the possibility of increasing the sensitivity of microbolometer detectors in the terahertz range by using an additional thin metal absorbing layer applied on the microbolometer membrane. A polarization dependence of the sensitivity of microbolometers in the terahertz and far infrared spectral ranges is found. It is shown that the sensitivity of microbolometers in the terahertz range is due to the absorption of radiation in the narrow metal runs placed on the support legs of the microbolometers and playing the role of an ohmic contact between the heat-sensitive layer and the processing curcuit.

Results of studies of the molecular beam epitaxial growth of HgCdTe alloys on Si substrates as large as 100 mm in diameter are presented. Optimum conditions for obtaining HgCdTe/Si(310) heterostructures of the device quality for the spectral range of 3–5 μm are determined. The results of measurements and discussion of photoelectric parameters of an infrared photodetector of a format of 320 × 256 elements with a step of 30 μm based on a hybrid assembly of a matrix photosensitive cell with a Si multiplexer are presented. A high stability of photodetector parameters to thermocycling from room temperature to liquid-nitrogen temperature is shown.

Two versions of silicon 1D multiplexer for 1 × 576 IR focal-plane arrays are designed, fabricated, and tested. The version LM-1 employs a direct-injection input circuit; the version LM-2 contains a buffered direct-injection circuit. They are intended for use with HgCdTe n +-p photodiodes operating in the wavelength ranges 8–14 and 3–5 μm, the minimum reverse diode resistance being 200 kΩ. The multiplexers ensure high uniformity of photodiode bias voltage; they are provided with a switched storage capacitance, which allows operation at different signal, background, and dark currents. Clocked at 3.5 MHz, they have an integration time of 40 μs and can read out 25 full-size (768 × 576) frames per second.

An infrared 320 × 256 focal plane array (FPA) for 7.5–10 μm was designed, fabricated and investigated. The photodetector matrix based on GaAs/AlGaAs quantum-well multilayer structures was grown by hydride epitaxy from organometallic compounds. The sensitivity peak was achieved at a wavelength of 9.3 μm and equaled 340 mA/W. The hybrid FPA was fabricated by cold welding indium bumps of the photodetector and silicon multiplexer. The obtained NETD was 29.4 mK at 68 K.

Principles of designing and functioning the 320 × 256 frame and row integration matrix multiplexers are considered. The temperature resolution of the MCT IR FPA and the designed multiplexers is analyzed.

The effect of dc current Idc on the electron transport in a GaAs quantum well with AlAs/GaAs superlattice barriers is studied experimentally at a temperature of 4.2 K in magnetic fields up to 2 T. A sharp increase in resistance Rxx is observed in magnetic fields higher than the critical field Bc. The value of Bc is found to decrease with increasing the current Idc. The phenomenon observed in the experiment is qualitatively explained by the electric breakdown of superlattice barriers under the action of the Hall field.

4 × 288 heteroepitaxial mercury–cadmium telluride (MCT) linear arrays for long wavelength infrared (LWIR) applications with 28 × 25 micron diodes and charge coupled devices (CCD) silicon readouts were designed, manufactured and tested. MCT heteroepitaxial layers were grown by MBE technology on (0 1 3) GaAs substrates with CdZnTe buffer layers and had cutoff wavelength λ co ≈11.8±0.15 μm at T =78 K. To decrease the surface influence of carrier recombination processes the compositionally dependent layers with increase of Cd content both toward the surface and HgCdTe/CdZnTe boundary interface were grown. Silicon readouts with CCD multiplexers with input direct injection circuits were designed, manufactured and tested. The testing procedure, to qualify readout integrated circuits on wafer level at T =300 K, was worked out. The silicon readouts for 4 × 288 arrays, with skimming and partitioning functions included were manufactured by n-channel MOS technology with buried or surface channel CCD register. The HgCdTe arrays and Si CCD readouts were hybridized by cold welding indium bumps technology. With skimming mode used for 4 × 288 MCT n–p-junctions, the detectivity for several tested 4 × 288 arrays was within D λ ∗ ≅9×10 10 –1.8×10 11 cm Hz 1/2 /W for background temperature T b =295 K.

A complete production technology is developed for single-cell and array IR detectors using an MBE-grown Hg1 – x Cd x Te heteroepitaxial layer. The array detectors implement a bump-bonded flip-chip hybrid architecture. The arrays are constructed in photodiodes and have a size of 128 × 128 or 4 × 288. The single-cell detectors are built around a photoconductivity cell. The detectors are operated in the wavelength range 3–5 or 8–12 μm and at 78–80 or 200–220 K. Some performance data on the detectors are presented.

Using Corbino disks with capacitance contacts, the microwave photoconductivity of the 2D electron gas in selectively doped GaAs/AlAs heterostructures has been studied at 4.2 K in magnetic fields up to 0.6 T. The giant oscillations of the magnetoconductivity have been revealed in the samples exposed to microwave radiation at high filling factors similar to those earlier discovered in the 2D Corbino disks with ohmic contacts. The results demonstrate that the presence of ohmic contacts is of no importance for the observation of the microwave-induced giant oscillations of the magnetoconductivity in the 2D electron system.

An electronic state with zero-differential conductance is found in nonlinear response to an electric field $E$ applied to two dimensional Corbino discs of highly mobile carriers placed in quantizing magnetic fields. The state occurs above a critical electric field $Eg{E}_{th}$ at low temperatures and is accompanied by an abrupt dip in the differential conductance. The proposed model considers a $local$ instability of the electric field $E$ as the origin of the observed phenomenon. Comparison between the observed electronic state and the state with zero differential resistance, occurring in Hall bar geometry, indicates that the nonlinear response of edge states and/or skipping orbits is not essential in the studied samples. The result confirms that quantal heating is the dominant nonlinear mechanism leading to electronic states with both zero differential resistance and conductance.

A photovoltaic detector design based on the graded band gap HgCdTe MBE structure with high conductivity layer (HCL) at interface, which provides photodiodes series resistance and a shortwave cut.off filter is developed. The optimal HCL parameters giving high quantum efficiency and minimal noise equivalent temperature difference were determined by calculations and experimentally confirmed. The hybrid 320×256 IR FPA operating in 8–12 μm spectral range was fabricated. The threshold power responsivity and minimal noise equivalent temperature difference values at wavelength maximum were 1.02×10−7 W/cm2, 4.1×108 V/W and 27 mK, respectively.

We developed high-frequency (HF) photodiodes (PD) and photoconductors (PC) operated in spectral range 1 - 20 ?m and frequencies over 1 GHz on the basis of HgCdTe heteroepitaxial structures (HS) with special composition distribution throughout the thickness grown on ZnCdTe/GaAs substrates by molecular beam epitaxy (MBE). The measurement HF PD and PC parameters were carried out. HF PD were used for study of subthermonuclear plasma.

The technology of high-quality microbolometer focal plane arrays (FPA) fabrication has been developed. Simple and cheap sol-gel technology of thermosensitive vanadium oxide layers preparation is underlain in its basis. Uncooled 160×120 microbolometer sensor assemblies for 8-14 microns spectral range have been fabricated. The paper brief outlines simple techniques to measure crosstalk, precision of FPA temperature stabilization and sensor assembly response time to infrared signal change. The noise equivalent temperature difference better than 100 mK has been achieved at frame rate 60 Hz and F/1 optics.

x4×288 heteroepitaxial mercury-cadmium telluride (MCT) linear arrays for long wavelength infrared (LWIR) applications with 28×25 micron diodes and charge coupled devices (CCD) silicon readouts were designed, manufactured and tested. MCT heteroepitaxial layers were grown by MBE technology on (013) GaAs substrates with CdZnTe buffer layers and have cutoff wavelength λco ≈ 11.8 μm at T = 78 K. To decrease the surface influence of the carriers recombination processes the layers with composition changes and its increase both toward the surface and HgCdTe/CdZnTe boundary were grown. Silicon read-outs with CCD multiplexers with input direct injection circuits were designed, manufactured and tested. The testing procedure to qualify read-out integrated circuits (ROICs) on wafer level at T = 300 K was worked out. The silicon read-outs for 4×288 arrays, with skimming and partitioning functions included were manufactured by n -channel MOS technology with buried or surface channel CCD register. Designed CCD readouts are driven with four- or two-phase clock pulses. The HgCdTe arrays and Si CCD readouts were hybridized by cold welding indium bumps technology. With skimming mode used for 4×288 MCT n-p-junctions, the detectivity was about (formula available in paper) for background temperature Tb = 295 K.© (2003) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

This paper presents the results of a study of the scientific and engineering principles of the creation of silicon multiplexers intended for reading out and preprocessing photodetector signals in the IR ranges 8–14 and 3–5 μm. The noise equivalent temperature difference is estimated for far-IR photodetectors based on silicon multiplexers with linewise and framewise accumulation of signals from HgCdTe photodiodes (PDs). The features of how the structural–technological limitations in the silicon readout circuits affect the characteristics of the IR photodetectors are analyzed for a wide range of parameters of HgCdTe PDs and a wide range of technological design norms for fabricating silicon multiplexers.

For manufacture of focal plane arrays (FPA) the MBE grown heteroepitaxial structures GaAs/CdZnTe/CdHgTe with cut-off wavelength ((lambda) c) of 6.0 and 8.7 micrometers were used. The photosensitive CdHgTe layer was grown with special composition profile in depth being continuously controlled in the growth process. On these structures by the method of low temperature planar technology the 128x128 photodetector arrays were manufactured, including the ones with low series resistance for the far IR range. The read-out circuit was designed and silicon array multiplexers were manufactured CMOS technology with n- pocket. The read-out circuit allows to control the accumulation time at a fixed frame time. The technology of hybrid assembling with continuous control over cold welding on indium bumps was designed and the 128X128 FPAs were fabricated by means of this technology. The noise-equivalent difference of temperature (NEDT) value was 19.7 and 27.2 mK for modules with (lambda) c=6.0 micrometers and 8.7 micrometers correspondingly at the background temperature 77K. Using the IR camera the examples of IR images obtained by the fabricated FPAs with the 128x128 frame format are demonstrated.

In this paper the experimental results on designing of 128X128 FPA for far IR spectrum range are presented. The module is a hybrid assembly of the photodetectors array based on GaAs/AlGaAs multiquantum wells and silicon multiplexer. The noise equivalent difference of temperature of the photodetector module NEDT=0.067 K at T=65 K.

The technology was developed and 128x128 LWJR FPA's based on HgCdTe epitaxial layers MBE-grown on GaAssubstrates with cutoff wavelength X = 8 tm and 13 m was fabricated. The photosensing layer HgCdTe was graded-gaplayer with the higher content of Cd to boundaries of a layer. The manufactured LWIR FPA's had NETD 32 inK and l7mKfor X 8 pm and 13 pm, correspondingly, at 295K background and 80K operation temperatures.KEYWORDS: HgCdTe, MBE layer, LWIR focal plane array, graded-gap layers 1. INTRODUCTION By now, HgCdTe is a basic material for far band JR arrays'. The high quantum efficiency of HgCdTe photodetectors favorably distinguishes them from GaAs/A1GaAs detectors based on quantum wells and superlatties, the PtSiShottky diodes and heterostructures on GeSi/Si2. The high technology level allows to manufacture two-color photodetectorsfor various spectral range in one work cycle3. The MBE technique permit to control the change in layer composition ingrowth prosess, that allows to adjust physical and photoelectric photodetector parameters4.The present paper describes the technology of HgCdTe growth on GaAS substrate by MBE method, the 128x128photodetector arrays and readout circuit manufacture and LWIR FPAs hybrid assembly. The parameters of hybrid FPAswith cutoffwavelengths 13 tm and 8 .tm are represented and the examples ofthe thermal images are given.

This paper discusses the process-design principles for creating hyperlarge-format mosaic photodetectors (MPDs), based on the butt-joining process of silicon chips with uncooled small-format microbolometer detector arrays (MBDAs). The basic unit is investigated and optimized for the process operations of laser scribing as part of the high-precision butt-joining process of chips in which the process part of the blind zone between the photosensitive edge elements of adjacent MBDA chips has a total size no greater than 30 μm. The design and layout are synthesized for 384×288-format silicon multiplexers, from which a 3072×576-format MPD fabricated using the butt-joining process developed here can provide better than 99% image-conversion efficiency for IR microbolometers and up to 100% for terahertz-range microbolometers.

Heterostructures HgCdTe/CdTe/GaAs grown by molecular beam epitaxy were used for LWIR FPA fabrication. The technology was developed and 32 by 32 and 128 by 128 photodiode arrays with indium bumps of 15 micrometer height in each pixel were fabricated. Mean NEP is 1.7 by 10-13 W/Hz1/2 and 1.1 by 10-14 W/Hz1/2 for 128 by 128 photodiode arrays with (lambda) c value of 10.4 micrometer and 5.2 micrometer correspondently. The technology of hybrid assembling with continuous control of cold welding on the measuring stand was demonstrated on the example of 32 by 32 LWIR FPA. Mean NEP value of 5.4 by 10-14 W/Hz1/2 with (lambda) c equals 10.6 micrometer at 80 K operation were obtained. using an infrared camera system the infrared image was successfully demonstrated. The NETD value of 0.077 K was obtained under 293 K background condition.

Current induced oscillations of differential conductivity of two-dimension electrons, placed in quantizing magnetic fields, are observed in GaAs quantum wells in Corbino geometry. The oscillations are periodic in the square of the inverse magnetic field and occur in Corbino rings with a width which is much lesser than the radius of the rings. The conductance oscillations are described by Zener tunneling between Landau orbits in the absence of the Hall electric field.

Microwave induced photoconductivity of a two-dimensional electron gas (2DEG) in selectively-doped GaAs/AlAs heterostructures has been studied using the Corbino geometry with capacitive contacts at a temperature T=1.6K and magnetic field B up to 0.5 T. Zero-conductance states have been observed in the samples under study subject to microwave radiation, similarly to the samples with ohmic contacts. It has been shown that ohmic contacts do not play a significant role for observation of zero-conductance states induced by microwave radiation

This paper proposes a photodetector design based on a CdHgTe variband heteroepitaxial structure with a high-conductivity layer (HCL) that ensures that the photodiodes have low series resistance and simultaneously serves the function of a short-wavelength cutoff filter. Based on an analysis of how the parameters of the HCL affect the quantum efficiency and the noise-equivalent temperature difference of the photodetector arrays (PDAs), its optimum parameters are determined. Samples of PDAs are fabricated with a format of 320×256 elements for the 8-12-μm spectral range, based on hybrid assembly of photosensitive elements made from p-type (013) HgCdTe/CdTe/ZnTe/GaAs heteroepitaxial structures with an HCL and a silicon multiplexer. The voltage sensitivity, the threshold irradiance, and the noise-equivalent temperature difference at the maximum sensitivity were 4.1×108V/W, 1.02×10−7W/cm2, and 27mK, respectively.

The initial plane-parallel position of a photodetector array (PDA) and a silicon multiplexer (MUX) is brought about when the tops of the indium microposts are in contact under the action of only the force of gravity on the PDA. We orient the crystals (along xy) in visible light, and we use offset reference marks on the PDAs. We bring chains of laser microholes in the polyimide of the offset reference marks into coincidence with the reference marks on the MUX. We take into account the initial errors of all the axial lines; the alignment error reaches +/-0.4μm (along xy). At all stages of the assembly, the MUX is connected, and we observe the touching and the welding of the microposts. To avoid warping the planar transistors (along z), we use stops of suitable height, placed along the perimeter of the PDA.

This paper presents the results of the development of linear (1×288, 1×576) and two-dimensional (128×128, 320×256) silicon multiplexer arrays for HgCdTe photodiodes of the 8-16μm spectral range. Typical parameters of the multiplexers are given, along with the characteristics of long-wavelength hybrid IR photodetectors created at the Institute of Semiconductor Physics of the Siberian Section of the Russian Academy of Sciences.

A theory for the admittance spectroscopy (AS) to study deep levels in surface-barrier structures with nonuniform distribution of impurities is developed. A procedure of treating experimental data to determine energy positions of levels, their capture cross-sections, as well as the Concentration profiles is described. The effect of various factors on AS resolution is discussed. [Russian Text Ignored].

Distribution profiles for the levels of radiation defects in hyperabrupt implanted p+-n junctions irradiated by electrons with a dose up to 5 × 1015 cm−2 are studied using admittance spectroscopy (AS). Besides a general tendency of the defect density to decrease towards the surface, the distribution of defects is shown to be correlated with the profile of the doping impurity (phosphorus). It is associated with the reduced energy of defect formation in the layer implanted. The effect is measured of an electric field ranging within e ≈ 104 to 5 × 105 V/cm on the activation energy E for the emission rate of electrons from A- and E-centers. It is found that E(e) dependences obtained using the AS method differ significantly from those observed usually in DLTS experiments. [Russian Text Ignored].