Showing papers on "Mercury cadmium telluride published in 1995"
Book•
01 Dec 1995
TL;DR: In this paper, Mercury cadmium telluride: growth mechanical and thermal properties dielectric and optical properties diffusion defects band structure and carrier properties surfaces and interfaces exploitation in devices.
Abstract: Part 1 Mercury cadmium telluride: growth mechanical and thermal properties dielectric and optical properties diffusion defects band structure and carrier properties surfaces and interfaces exploitation in devices. Part 2 CdTe/CdZn Te/CdTeSe.
397 citations
TL;DR: In this paper, a new etch system is described which produces pits on the technologically important B face of (111) and (211) CdTe and CdZnTe which are commonly used in mercury cadmium telluride (MCT) epitaxy.
Abstract: A new etch system is described which produces pits on the technologically important B face of (111) and (211) CdTe and CdZnTe which are commonly used in mercury cadmium telluride (MCT) epitaxy A ratio of approximately 10 wide: 1 deep is achieved with this etch allowing its use without removing excessive material Examples of the use of this etch are given and a comparison is made with the Nakagawa, A face etch system which is in common use to characterize this family of materials A screening protocol is discussed which integrates the use of etch pitting into the manufacture of substrates for use in epitaxial MCT applications Comparisons are made between CdZnTe substrates grown using the horizontal and vertical Bridgman techniques
143 citations
06 Jun 1995
TL;DR: The first prototype of a HgCdTe infrared detector array with 1024 X 1024 pixels developed by the Rockwell International Science Center has been tested in a new infrared camera at the UH 2.2 m telescope, the 0.6 m telescope and the CFHT as discussed by the authors.
Abstract: The first prototype of a HgCdTe infrared detector array with 1024 X 1024 pixels developed by the Rockwell International Science Center has been tested in a new infrared camera at the UH 2.2 m telescope, the 0.6 m telescope, and the CFHT. At the 2.2 m tests were conducted both at f/31, where images of very high resolution were obtained using tip-tilt correction, and at f/10 for a wide field of view. At the CFHT both wide field imaging (f/8) and adaptive optics work was done. The HAWAII (HgCdTe astronomical wide area infrared imager) prototype device achieved very good performance. In the camera system, a double correlated readnoise of 15 e - rms was achieved. The dark current at 1 V bias could be confirmed to be below 1 e - , even though the device was operated above 77 K. The quantum efficiency is slightly below 50% and shows the wavy pattern characteristic of LPE-grown HgCdTe. The full well capacity is above 10 5 e - at 1 V bias, limited in our system by the dynamic range of the A/D converter. Data reduction is practically identical to what is used for NICMOS3 256 X 256 devices. Combined integration times of more than 1 hour have been used and demonstrate that the HAWAII devices are suitable for very deep imaging. The residual excess dark current problem known from NICMOS3 devices is not fully resolved. However, it appears less serious in our first HAWAII prototype device.
16 citations
TL;DR: In this article, the growth rates, layer thickness, and morphology for both ZnTe and CdTe buffer layers were monitored using a pyrometer which was sensitive to the 2.6 μm waveband and accurate to ± 1°C.
Abstract: Reproducible improvements in the metalorganic vapor phase epitaxy (MOVPE) grown CdTe buffer quality have been demonstrated in a horizontal rectangular duct silica reactor by the use of integratedin situ monitoring that includes laser reflectometry, pyrometry, and Epison concentration monitoring. Specular He-Ne laser reflectance was used toin situ monitor the growth rates, layer thickness, and morphology for both ZnTe and CdTe. The substrate surface temperature was monitored using a pyrometer which was sensitive to the 2–2.6 μm waveband and accurate to ±1°C. The group II and group VI precursor concentrations entering the reactor cell were measured simultaneously using two Epison ultrasonic monitors and significant variations were observed with time, in particular for DIPTe. The surface morphology and growth rates were studied as a function of VI/II ratio for temperatures between 380 and 460°C. The background morphology was the smoothest for VI/IIratio in the vicinity of 1.5–1.75 and could be maintained using Epison monitors. Regularly shaped morphological defects were found to be associated with morphological defects in the GaAs/Si substrate. The x-ray rocking curve widths for CuKα (531) reflections were in the range of 2.3–3.6 arc-min, with no clear trend with changing VI/II ratio. X-ray topography images of CdTe buffer layers on GaAs/Si showed a mosaic structure that is similar to CdTe/sapphire substrates. The etch pit density in Hg1-xCdxTe layers grown onto improved buffer layers was as low as 6 x 106 cm-2 for low temperature MOVPE growth using the interdiffused multilayer process.
15 citations
TL;DR: In this article, the use of spectroscopic ellipsometry for monitoring the vapor phase epitaxial growth of mercury cadmium telluride (Hg1−xCdxTe) in real-time is demonstrated.
Abstract: The use of spectroscopic ellipsometry for monitoring the vapor phase epitaxial growth of mercury cadmium telluride (Hg1−xCdxTe) in real-time is demonstrated. The ellipsometer is used to perform system identification of the chemical vapor deposition reactor used for the growth of CdTe and to measure the response of the reactor to different growth conditions. The dynamic behavior of the reactor is also studied by evaluating the gas transport delay. The optical constants of Hg1−xCdxTe are determined at the growth temperature for different compositions.In-situ real-time composition control is performed during the growth of Hg1−xCdxTe. The required target compositions are attained by the ellipsometer and appropriate corrections are also made by the controller when a noise input in the form of a temperature variation is introduced.
14 citations
29 Sep 1995
TL;DR: In this paper, the authors describe a 10-channel infrared (1.27 to 16.9 micrometers ) radiometer instrument known as SABER (sounding of the atmosphere using broadband emission radiometry) that will measure earth-limb emissions from the TIMED (thermosphere ionosphere-mesosphere energetics and dynamics) satellite.
Abstract: This paper describes the design of a 10-channel infrared (1.27 to 16.9 micrometers ) radiometer instrument known as SABER (sounding of the atmosphere using broadband emission radiometry) that will measure earth-limb emissions from the TIMED (thermosphere- ionosphere-mesosphere energetics and dynamics) satellite. The instrument telescope, designed to reject stray light from the earth and the atmosphere, is an on-axis Cassegrain design with a clam shell reimager and a one-axis scan mirror. The telescope is cooled below 210 K by a dedicated radiator. The focal plane assembly (consisting of a filter array, a detector array, a Lyot stop, and a window) is cooled to 75 K by a miniature cryogenic refrigerator. The conductive heat load on the refrigerator is minimized by a Kevlar support system that thermally isolates the focal plane assembly from the telescope. Kevlar is also used to thermally isolate the telescope from the spacecraft. Instrument responsivity drifts due to changes in telescope and focal plane temperatures as well as other causes are neutralized by an in-flight calibration system. The detector array consists of discrete HgCdTe, InSb, and InGaAs detectors. Two InGaAs detectors are a new long wavelength type, made by EG&G, that have a long wavelength cutoff of 2.33 micrometers at 77 K.
12 citations
NEC1
TL;DR: In this article, a hybrid HgCdTe 256 by 256 FPA for LWIR detection was fabricated and an infrared image was demonstrated, where epilayers were grown on GaAs substrates by MBE and annealed to p-type.
Abstract: A hybrid HgCdTe 256 by 256 FPA for LWIR detection was fabricated and an infrared image was demonstrated. MCT epilayers were grown on GaAs substrates by MBE and annealed to p- type. The n+ on p photodiodes were formed by boron ion implantation. The mean value of zero bias differential resistance for the diode array was measured to be 8.0 M(Omega) with a cutoff wavelength of 9.5 micrometer. The effective quantum efficiency was estimated to be 0.55, and the optical cross talk was estimated to be 8.2%. A multiline parallel integration readout circuit designed especially for this 256 by 256 LWIR FPA, had 8.3 X 107 electron capacity, a 190 microsecond integration time, and a single output. This work shows that the MBE growth method on GaAs substrates, pn junction formation process, the MLPI circuit design, and the hybridization technique are useful technologies.© (1995) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
9 citations
31 May 1995
TL;DR: In this paper, the advantages of measuring open-path Fourier transform infrared (OP/FT-IR) spectra at low resolution were discussed both from a theoretical and experimental viewpoint, and the optimum combination of selectivity and sensitivity was found when the resolution is approximately equal to the average fullwidth at half height (FWHH) of the analytical bands.
Abstract: The advantages of measuring open-path Fourier transform infrared (OP/FT-IR) spectra at low resolution are discussed both from a theoretical and experimental viewpoint In general, the optimum combination of selectivity and sensitivity is found when the resolution is approximately equal to the average full-width at half height (FWHH) of the analytical bands The FWHH of many bands in the vapor-phase spectra of molecules of medium size, such as chlorinated organic solvents, is approximately 20 cmMIN1, so that a resolution of 16 cmMIN1 is often found to yield the most accurate analytical results The low baseline noise level found when spectra are measured at low resolution can allow room temperature deuterated triglycine sulfate pyroelectric bolometers to be used instead of liquid nitrogen cooled mercury cadmium telluride photodetectors for OP/FT-IR measurements© (1995) COPYRIGHT SPIE--The International Society for Optical Engineering Downloading of the abstract is permitted for personal use only
9 citations
24 Apr 1995
TL;DR: In this article, an overview of the issues related to quantum well and superlattice IR detectors and their application in space missions is presented. But the authors do not discuss in detail the application of these detectors for space missions.
Abstract: Quantum well and superlattice IR detectors have recently become visible contenders for many military applications. In this paper we present an overview of the issues related to quantum well and superlattice IR detectors and discuss in detail, the issues related to the application of these detectors for space missions.
7 citations
08 Sep 1995
TL;DR: In this paper, a 256 x 256-element HgCdTe hybrid infrared focal plane array (IRFPA) for the 8 to 10 j.tm band was developed.
Abstract: We developed a 256 x256element HgCdTe hybrid infrared focal plane array (IRFPA) for the 8 to 10 j.tm band. We usedthree technologies to develop this high-performance, long-wavelength, large-scale IRFPA. The first innovation was to glue a sapphire substrate to a thinned Si readout circuit to reduce the thermal expansion mismatch with a HgCdTe diode arrayfabricated on a CdZnTe substrate. The second was to fabricate an interlaced switched-FET readout circuit using a 3 im CMOS process. This readout circuit has a storage capacity of more than iO electrons and two video outputs capable of a 3.5 MHz data rate. The third was a HgCdTe diode array with an anodic sulfide passivation film and an optimized cutoff wavelength to reduce dark current and achieve high sensitivity. The noise equivalent temperature difference (NETD) was 0.06 K using f/2.5 optics. After 1000 thermal cycles (300 K-80 K), there were no significant indium bump failures nor notable degradation in detector performance.Keywords: IRFPA, HgCdTe, 256 x 256 element, 8-10 im band, Switched-FET, CMOS, Si readout circuit, NETD1. INTRODUCTIONHgCdTe is a commonly used material for JR detectors due to its high quantum efficiency, especially for the 8 to 10 tmband. Hybrid IRFPAs consisting of HgCdTe photovoltaic (PV) diode arrays and Si readout circuits will be increasingly usedin future high-performance JR imaging devices. Recently, much effort has been directed to large-scale IRFPAs to improvethe resolution. Large-scale HgCdTe hybrid IRFPAs with a high sensitivity for the 3 to 5 im band have been demonstrated in
7 citations
08 Sep 1995
TL;DR: In this article, the authors describe pyroelectric device trade-offs, architecture, and process of the TH 7441A 128 by 128 area array infrared detector, based on the interline architecture.
Abstract: P(VF2-TrFE) pyroelectric copolymer is chosen for its high level of compatibility with existing microelectronics processes, and convenient electrical properties for infrared (IR) 8 to 14 micrometer imagery in the performance range of NETD 0.1 K to 1 K. Low cost sensors, achievable thanks to the monolithic silicon wafer processing, standard package assembly, and uncooled operations, allow us to address a lot of low-end applications in which conventional IR imaging techniques -- high priced hybrid mercury cadmium telluride or indium antimonide arrays, liquid nitrogen cooling and sophisticated image processing -- are nowadays incompatible with large volume user's needs and market prices. The paper describes pyroelectric device trade-offs, architecture, and process. Based on the interline architecture, the sensor performances of the TH 7441A 128 by 128 area array infrared detector are presented: compatible with 1 inch optics, the square array is made of an 80 by 80 micrometer squared pixel, on a pixel pitch of 85 micrometer. The CCD multiplexer using patented on-site processing is designed to deliver the image information at the maximum rate of 50 image/s. Lower rates are achievable. Imaging performances are the following: a NETD of 1.7 K is achieved with an integration time of 10 ms and the use of a f/1 optics presenting a transmission of 0.8. Recent improvements in the properties of the pyroelectric sandwich include thermal insulation of the pyroelectric layer through mixed air-polyimide material and pixel side to side insulation. Thanks to on-wafer pixel reticulation, an increased modulation transfer function of 51% at Nyquist frequency is achieved.© (1995) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
01 Sep 1995
TL;DR: An etch process was developed to determine the dislocation density on B - Hg1-xCdxTe-epilayers grown by liquid phase epitaxy from a tellurium-rich solution as discussed by the authors.
Abstract: An etch process was developed to determine the dislocation density on B - Hg1-xCdxTe-epilayers grown by liquid phase epitaxy from a tellurium-rich solution. A correlation between the etch pit density and the Cd1-yZnyTe-substrate material properties is found. Additionally the yield of photovoltaic diode performance strongly depends on the value of these measured dislocation densities. This method acts as a pass/fail evaluation for the epilayers used in our infrared device fabrication.© (1995) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
12 Sep 1995
TL;DR: In this paper, a simple empirical rule for the absorption coefficient of MCT was proposed, valid both in the non-degenerate and in the degenerate case, taking into account the Urbach band tailing and non-parabolicity of bands.
Abstract: In this work we propose a simple empirical rule for the absorption coefficient of mercury cadmium telluride (MCT), valid both in the non-degenerate and in the degenerate case. The rule takes into account the Urbach band tailing and non-parabolicity of bands. Additionally, an expression is proposed for the Moss-Burstein effective bandgap spreading in degenerate narrow-band semiconductors. The results are compared to the available experimental data on MCT and to the results of numerical calculation obtained by the Kane model. A critical comparison is made between the proposed rules and the standard approximations used to describe the MCT absorption coefficient.
29 Sep 1995
TL;DR: In this paper, the structure of the infrared focal plane for the AIRS instrument has been defined and is presented in this paper, which leads to a focal plane assembly of 53 mm by 66 mm, the largest ever built at LIRIS.
Abstract: AIRS is a key facility instrument on the first post meridian platform as part of NASA'a Earth Observing System (EOS) program. The Atmospheric Infrared Sounder measurement technique is based on passive IR remote sensing using a high spectral resolution grating spectrometer. The structure of the infrared focal plane for the AIRS instrument has been defined and is presented in this paper. The optical footprint of 8.1 mm by 36.3 mm along with the necessary support and interface components leads to a focal plane assembly of 53 mm by 66 mm, the largest ever built at LIRIS. With 4208 diodes and 274 photoconductors in the same focal plane to achieve the wide spectral coverage from 3.7 to 15.4 micrometers , a modular approach is required. Ten PV modules utilize silicon readout integrated circuits (ROICs) joined to the detector arrays as either direct or indirect hybrids while two PC modules cover the 13.7 to 15.4 mm range, optically chopped and led out to uncooled preamplifiers. The simultaneous operation of PV and PC devices in the same focal plane has required unique approaches to shielding, ROIC output design and lead routing. High D*'s of 7E14 and 3E11 cm- Hz1/2/W are needed to meet the sensitivity requirements of the 4.2 and 15.0 micrometers regions respectively. The 35 micrometers by 800 micrometers PC detectors on a 50 micrometers pitch have necessitated modifications to standard delineation techniques, while the MW performance is nearly D* BLIP for PV devices. Dispersed energy is presented to the modules through 17 narrow band filters packaged into a single precision assembly mounted within 0.18-0.25 mm of the focal plane surface. The more than 50 components comprising the focal plane in conjunction with the tightly spaced optical pattern presented by the grating add a high degree of complexity to the assembly process. This paper focuses on the architectural constraints derived from performance, interface, and reliability requirements. Key aspects of these requirements are presented and their impact on the partitioning of the 12 modules is discussed. The rationale for the spectral range assigned to each module is reviewed relative to PV and PC performance capabilites. ROIC design guidelines and physical contraints due to manufacturability and assembly. Results of structural and thermal analyses for the various module configurations and assembled focal plane to determine compliance with the stringent stability and positional requirements are presneted. Specific features of the module carrier/interface boards and the multilayered focal plane carrier/interface board are included as well as a review of the overall assembly sequence of the focal plane as influenced by repairability and reliability considerations. The comprehensive redundance strategy applied to the design of the FPA/dewar assembly will be reviewed, and the approach for operation/survival in the radiation environment is discussed. Key features of the ROIC, PV, and PC array designs will be presented along with results of analyses performed.
TL;DR: In this article, the development of ISOVPE was presented, giving a complete theoretical model of the process, which is based on fundamental results in the field of phase diagrams of the (Hg,Cd)Te the interdiffusion of Hg and Cd, gas-phase transport, etc.
Abstract: Isothermal vapour-phase epitaxy (ISOVPE) was the earliest process to be developed for the fabrication of epitaxial mercury-cadmium telluride layers. Although the process was somewhat neglected in the previous period, mostly because of the appearance of metalorganic chemical vapour phase epitaxy and molecular-beam epitaxy, the results of the most recent investigations show that the application of this method can be expected in the second generation of photovoltaic (PV) or metal-insulator-semiconductor (MIS) detectors in the focal plane. This review paper presents the development of ISOVPE giving a complete theoretical model of the process, which is based on fundamental results in the field of phase diagrams of the (Hg,Cd)Te the interdiffusion of Hg and Cd, gas-phase transport, etc. Using the results of this theoretical model, a production system for ISOVPE was designed, in which the deposition process, the high-temperature annealing for composition homogenization and the low-temperature annealing for the achievement of the desired epitaxial-layer doping are all performed in the same cycle. Finally, the basic electrical and optical characteristics of ISOVPE layers are analysed. It is shown that in applications of the fabrication of PV and MIS detector arrays a full affirmation of this technology can be expected.
08 Sep 1995
TL;DR: In this article, the effect of doping profiles on the photodiode parameters (RoA product, I-V characteristic, photoelectrical gain and noise) is solved by forward-condition steady-state analysis.
Abstract: The performance of long wavelength infrared (LWIR) n+-on-p HgCdTe photodiodes is re-examined theoretically. It is assumed that the performance of photodiodes is due to thermal generation governed by the auger mechanism. The investigations are carried out for photodiodes operated in temperature range between 300 and 50 K. The effect of doping profiles on the photodiode parameters (RoA product, I-V characteristic, photoelectrical gain and noise) is solved by forward-condition steady-state analysis. The theoretical predictions of photodiode parameters are compared with experimental data obtained by the research group at the LETI. Excellent agreement between both types of results indicate that experimentally measured performance of n+-on-p HgCdTe LWIR photodiodes are determined by the auger thermal generation mechanism.© (1995) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
16 Oct 1995
TL;DR: In this paper, the authors compared several key infrared detector technologies versus operating temperature and background flux via hybrid FPA test at operating temperatures from 32.5 K to room temperature and photon backgrounds from mid-105 to approximately equal to 1017 photons/cm2-sec.
Abstract: We compare several key infrared detector technologies versus operating temperature and background flux via hybrid FPA test at operating temperatures from 32.5 K to room temperature and photon backgrounds from mid-105 to approximately equal to 1017 photons/cm2-sec. The detector materials include photovoltaic (PV) HgCdTe/Al2O3, PV HgCdTe/CdZnTe, photoconductive (PC) GaAs/AlGaAs quantum well infrared photodetector (QWIP) and PV InGaAs/InP; the device sizes range from 64 multiplied by 64 to 1024 multiplied by 1024.© (1995) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
01 Sep 1995
TL;DR: In this paper, the authors used molecular-beam epitaxy (MBE) to deposit single crystal epitaxial films of CdTe (112)B and HgCdTe(112)C directly onto Si(112), without the use of GaAs interfacial layers.
Abstract: Molecular-beam epitaxy (MBE) has been utilized to deposit single crystal epitaxial films of CdTe(112)B and HgCdTe(112)B directly onto Si(112) substrates without the use of GaAs interfacial layers. The films have been characterized with x-ray diffraction and wet chemical defect etching, and IR detectors have been fabricated and tested. CdTe(112)B films are twin- free and have x-ray rocking curves as narrow as 72 arc-seconds and near-surface etch pit density (EPD) of 2 X 106 cm-2 for 8 micrometers -thick films. HgCdTe(112)B films deposited on Si substrates have x-ray rocking curve FWHM as low as 92 arc-seconds and EPD of 8 - 30 X 106 cm-2. HgCdTe/Si infrared detectors have been fabricated with R0A equals 4.3 X 103 (Omega) -cm2 (f/2 FOV) and 7.8 micrometers cutoff wavelength at 78 K to demonstrate the capability of MBE for growth of large-area HgCdTe arrays on Si.© (1995) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
TL;DR: In this paper, the noise-equivalent-temperature difference (NETD) is calculated in fixed-pattern-noise-limited mercury cadmium telluride (MCT) focal-plane arrays (FPA5) for both 3-to 5-μm and 8-to 14-mm terrestrial imaging applications, on the basis of a model for MCT in which a linear two-point compensation scheme is considered.
Abstract: The noise-equivalent-temperature difference (NETD) is calculated in fixed-pattern-noise-limited mercury cadmium telluride (MCT) focal-plane arrays (FPA5) for both 3- to 5-μm and 8- to 14-μm terrestrial imaging applications, on the basis of a model for MCT in which a linear two-point compensation scheme is considered. The contributions to the NETD from the fixed-pattern noise of an array-in terms of gain, offset, and residual error-are calculated and taken in quadrature to obtain the NETD of the FPA. The effect of stability of the focal-plane temperature is included, but the contribution of readout is not considered. The largest contribution to the NETD is from the residual error in the compensation scheme. Decreasing the intrascene temperature difference and including a sharp-cutoff filter are shown to decrease the NETD. The composition has been varied so as to obtain the lowest NETD in each band: at x = 0.31 in the 3- to 5-μm band, and at x = 0.22 to 0.23 in the 8- to 14- μm band (where x is the composition in the alloy Hg 1- x Cd x Te).
TL;DR: Theoretical expressions to calculate the signal-to-noise ratio of an IR detector in a direct injection readout hybrid focal plane array (FPA) are developed in this article.
15 Sep 1995
TL;DR: In this paper, the authors proposed a coherent camera based on optical heterodyne interferometry, which can provide spectral and range information for target surveillance, range detection, chemical plume evolution, monitoring stack plume emissions, and wind shear detection.
Abstract: New developments in 2-D, wide-bandwidth HgCdTe (MCT) and GaAs quantum-well infrared photodetectors (QWIP) coupled with Monolithic Microwave Integrated Circuit (MMIC) technology are now making focal plane array coherent infrared (IR) cameras viable. Unlike conventional IR cameras which provide only thermal data about a scene or target, a coherent camera based on optical heterodyne interferometry will also provide spectral and range information. Each pixel of the camera, consisting of a single photo-sensitive heterodyne mixer followed by an intermediate frequency amplifier and illuminated by a separate local oscillator beam, constitutes a complete optical heterodyne receiver. Applications of coherent IR cameras are numerous and include target surveillance, range detection, chemical plume evolution, monitoring stack plume emissions, and wind shear detection.
Patent•
31 Jan 1995
TL;DR: In this article, the authors proposed a method to control the composition and doping concentration of a cell source by controlling the composition of a tellurium cell source and a cadmium arsenide compound cell source.
Abstract: PURPOSE:To control composition and doping concentration, with growth parameters as few as posibble, by controlling the composition of mercury cadmium telluride and the doping concentration of arsenide, on the basis of the temperature control of a tellurium cell source and a cadmium arsenide compound cell source. CONSTITUTION:Mercury, tellurium, and cadmium arsenide are used as row materials of cell source for crystal growth. In the state that the temparatures of cell sources 3-5 are controlled, mercury and tellurium are indivually evaporated from a mercury cell source 3 and a tellurium cell source 4, and further cadmium which contributes to growth and arsenic which is led in a growth layer are simultaneously evaporated from a cadmium arsenide compound cell source 5. On the basis of the temperature control of the tellurium cell source 4 and the cadmium arsenide compound cell source 5, the composition of the mercury cadmium telluride and the doping concentration of arsenic are controlled. For example, the temperature of the cadmium arsenide compound cell source 5 is adjusted at about 200-400 deg.C.
30 May 1995
TL;DR: In this paper, the fluence of pulsed lasers of wavelength 4 and 10.6 microns was calculated and the R0A values of HgCdTe were obtained by simultaneously including generation-recombination, diffusion and tunneling mechanisms.
Abstract: The fluence of pulsed lasers of wavelength 4 and 10.6 microns necessary to induce one and two orders of magnitude temporary degradation in the R0A values of Hg0.7Cd0.3Te p/n infrared detectors at 100 K, and Hg0.78Cd0.22Te p/n infrared detectors at 40 K have been calculated. A nonparabolic energy-momentum relationship and temperature dependent energy gap of HgCdTe were used in this calculation. The R0A values used in this calculation were obtained by simultaneously including generation-recombination, diffusion and tunneling mechanisms.© (1995) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
TL;DR: In this paper, the SUMerCad simulator is used to simulate the interaction of native defects and dopants in Hg0.8Cd0.2Te in order to accurately model various processing techniques.
Abstract: Due to the large concentration of electrically active defects in Hg1-xCdxTe, it is important to properly account for them when designing fabrication processes for infrared focal plane arrays (IRFPAs). Stanford University’s Mercury Cadmium Telluride Process Simulator, SUMerCad, is being developed to simulate the interaction of native defects and dopants in Hg0.8Cd0.2Te in order to accurately model various processing techniques. Non-linear coupled differential equations are used to model the physics of the diffusion mechanisms, rather than extrapolating the diffusion profiles from experimental data. The fundamental constants for the point defects were obtained by exercising the simulator over the various parameter spaces and comparing the results to experimental work and best principle calculations. The methodologies used, point defect mechanisms modeled, and parameters determined are discussed.
TL;DR: In this article, the authors have discussed the issues and processes for fabrication of mercury cadmium telluride detector arrays, charge coupled device readout arrays and integration of these into a focal plane array sensor.
Abstract: Technological issues and Processes for fabrication of mercury cadmium telluride detector arrays, charge coupled device readout arrays and integration of these into a focal plane array sensor have been discussed. Mini arrays of 16 X 16 size have been realised and tested to prove the technology and process schedule with a view to scaling up this for larger arrays to be used in the antitank guided missile.
01 Sep 1995
TL;DR: In this paper, the electrical and optical properties of iodine-doped n-type CdTe and HgCdTe alloys and superlattices grown by metalorganic molecular beam epitaxy using ethyliodide are reviewed.
Abstract: The electrical and optical properties of iodine doped n-type HgCdTe alloys and superlattices grown by metalorganic molecular beam epitaxy using ethyliodide are reviewed. The rationale for the use of iodine rather than indium as the dopant species and the incorporation kinetics of iodine at the growth surface are discussed. The electrical and optical properties of iodine- doped CdTe and HgCdTe (x equals 0.24) are presented for carrier concentrations between 1015 and 1018 cm-3, as determined by Hall effect measurements and low- and room-temperature photoluminescence spectroscopy. These samples show strong room temperature excitonic effects due to free exciton and band to band recombination as determined by photoluminescence excitation spectroscopy. The electrical and optical properties of iodine-doped HgCdTe-CdTe superlattices also are discussed based on magnetoluminescence measurements in tilted magnetic fields of up to 7 Tesla in Voigt and Faraday geometry.© (1995) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
03 Nov 1995
TL;DR: In this article, the authors investigated the influence of macrodefect's and isovalent admixture's influence on photoluminescence spectra and halvanomagnetic parameters of CdTe/CdTe heterostructures.
Abstract: Mechanisms of macrodefect's and isovalent admixture's influence on photoluminescence spectra and halvanomagnetic parameters of HgCdTe/CdTe heterostructures were investigated. Profiles of electrical and structural parameter distributions through the depth of epilayers HgCdTe (x approximately equal to 0.2, p-type and with mixed conductivity), on CdTe substrates ('clean' and with 4% of Se or Zn components) were measured. There was detected substantial increase of well-known in CdTe donor-acceptor photoluminescence band 1.43 eV (T equals 77 K) in transition layers and CdTe substrates with increased macrodefect concentration (dislocations, subgrain boundaries, Te precipitates). It was established that such elevation was dealing with the donor component of conductivity in substrates and corresponding epilayers. The donor's nature was dealing with the substrate's defect structure. So photoluminescence band intensity may characterize CdTe defect level and permit us to reject such substrates.
01 Sep 1995
TL;DR: In this paper, a 2-inch Hg1-xCdxTe/Sapphire structures are grown by an isothermal vapor phase epitaxy process starting from MOCVD CdTe/sapphire hybrid substrates.
Abstract: High quality 2 inch Hg1-xCdxTe/Sapphire structures are grown by an isothermal vapor phase epitaxy process starting from MOCVD CdTe/Sapphire hybrid substrates. HgTe growth and CdTe/HgTe solid state interdiffusion processes produce the transformation of the starting CdTe layer into a compositionally controlled Hg1-xCdxTe film on the inert base sapphire substrate grown. By using experimental growth conditions involving HgTe/CdTe interdiffusion rates higher than HgTe growth rates, in depth compositionally uniform Hg1-xCdxTe films can be obtained in a really simple one-step process. A 2-zone open tube vertical reactor improved for 2 inch wafers has been used for the present process, making it very attractive for manufacturing purposes. Morphological, optical, electrical, and structural characteristics of the iso-VPE mercury cadmium telluride on sapphire structures are reported witnessing their technological power as infrared materials.© (1995) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
30 May 1995
TL;DR: In this paper, a flow process for the design, fabrication, and test methodologies for the production of linear long-wave infrared (LWIR) HgCdTe (MCT) detector arrays is described.
Abstract: We describe in this paper a flow process that details design, fabrication, and test methodologies for the production of linear longwave infrared (LWIR) HgCdTe (MCT) detector arrays. The modular manufacturing approach emphasizes testability in the component design and zero-loss procedure in the FPA assembly that achieved reliable, low-cost production of high performance scanning LWIR focal plane arrays. In-depth theory, practice, and automation of infrared detector array evaluation are also discussed.