V. S. Varavin

Bio: V. S. Varavin is an academic researcher from Russian Academy of Sciences. The author has contributed to research in topics: Molecular beam epitaxy & Photoluminescence. The author has an hindex of 14, co-authored 102 publications receiving 745 citations. Previous affiliations of V. S. Varavin include Russian Academy & Tomsk State University.

HgCdTe epilayers on GaAs: growth and devices

Abstract: View of basic and specific physical and chemical features of growth and defect formation in mercury cadmium telluride (MCT) heterostructures (HS's) on GaAs substrates by molecular beam epitaxy (MBE) was made. On the basis of this knowledge a new generation of ultra high vacuum set, ultra-fast ellipsometer of high accuracy and automatic system for control of technological processes was produced for reproducibility of MCT Hs's growth on substrates up to 4" in diameter. The development of industrially oriented technolgoy of MCT HS's growth by MBE on GaAs substrates 2" in diameter and without intentional doping is presented. The electrical characteristics of n-type and p-type of MCT HS's and uniformity of MCT composition over the surface area are excellent. The residual donor and acceptor centres are supposed as hypothetically tellurium atoms in metallic sublattice ("antisite" tellurium) and double-ionised mercury vacancies. The technology of fabricating focal plane arrays is developed. The high quality characteristics of infrared detectors conductance and diode mode are measured. Calculations of detector parameters predicted the improvement in serial resistance and detectivity of infrared diode detectors based on MCT heterostructures with graded composition throughout the thickness.

Molecular-beam epitaxy of mercury-cadmium-telluride solid solutions on alternative substrates

Abstract: Growth processes were considered for heteroepitaxial structures based on a mercury-cadmium-telluride (MCT) solid solution deposited on GaAs and Si alternative substrates by molecular-beam epitaxy. Physical and chemical processes of growth and defect-generation mechanisms were studied for CdZnTe epitaxy on atomically clean singular and vicinal surfaces of gallium-arsenide substrates and CdHgTe films on CdZnTe/GaAs surfaces. ZnTe single-crystalline films were grown on silicon substrates. Methods for reducing the content of defects in CdZnTe/GaAs and CdHgTe films were developed. Equipment for molecular-beam epitaxy was designed for growing the heteroepitaxial structures on large-diameter substrates with a highly uniform composition over the area and their control in situ. Heteroepitaxial MCT layers with excellent electrical parameters were grown on GaAs by molecular-beam epitaxy.

HgCdTe Heterostructures on Si (310) Substrates for Midinfrared Focal Plane Arrays

Abstract: 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.

Peculiarities of the MBE growth physics and technology of narrow-gap II-VI compounds

Abstract: Copyright (c) 1997 Elsevier Science S.A. All rights reserved. Experimental research and a crystallochemical consideration of the chemical interaction of the film and substrate components in the A 2 B 6 /GaAs heterostructure were carried out. It was found that surface faceting, twinning and breaking of stoichiometry of the growing structure can be explained by the excess of valent electrons at the A 2 B 6 /GaAs interface. The films were grown in a multichamber mercury cadmium telluride (MCT) MBE system with different compositions of the residual gas phase in different chambers. The MCT growth chamber is equipped with a system of molecular sources of original design and a built-in automatic ellipsometer. The used system of sources allows for growing MCT films without sample rotation, uniform in composition over the substrate area of 51 mm in diameter (the composition gradient does not exceed 0.002 cm −1 ). Because there is no substrate rotation, continuous measurements of film composition can be performed during growth, and structures with specified composition over thickness can be grown. The introduction of layers with a varying energy gap into the heteroepitaxial structure increases the carrier's lifetime up to 2 μs for x=0.22 (77 K). A model of defects, determining the electric parameters of MBE grown films in the presence of gallium sources, is suggested. Linear photoconductor arrays for the 8-12 μm band with background limited parameters were fabricated from the grown MCT films. © 1997 Elsevier Science S.A.

The growth of high-quality MCT films by MBE using in-situ ellipsometry

Abstract: The ellipsometry and RHEED study or high-quality MCT films grown on (112)- and (130) CdTe and GaAs by MBE was carried out. The dependenee of the ellipsometric parameter ψ on MCT composition is evaluated. It was shown that such parameters as growth rate, the surfaxe roughness, initial substrate temperature, and film composition may be measured by the in-situ ellipsometry. The appearance of surface roughness was observed in the initial stage of MCT growth under various compositious (x CdTe =40+0.4). The further growth at optimum conditions leads to the smoothing of the surface and supplies us with high-quality MCT films

HgCdTe infrared detector material: history, status and outlook

Abstract: This article reviews the history, the present status and possible future developments of HgCdTe ternary alloy for infrared (IR) detector applications. HgCdTe IR detectors have been intensively developed since the first synthesis of this material in 1958. This article summarizes the fundamental properties of this versatile narrow gap semiconductor, and relates the material properties to its successful applications as an IR photoconductive and photovoltaic detector material. An emphasis is put on key developments in the crystal growth and their influence on device evolution. Competitive technologies to HgCdTe ternary alloy are also presented. Recent advances of backside illuminated HgCdTe heterojunction photodiodes have enabled a third generation of multispectral instruments for remote sensing applications and have led to the practicality of multiband IR focal plane array technology. Finally, evaluation of HgCdTe for room temperature long wavelength IR applications is presented. (Some figures in this article are in colour only in the electronic version)

Fast, Self-Driven, Air-Stable, and Broadband Photodetector Based on Vertically Aligned PtSe2/GaAs Heterojunction

Abstract: This work shows the large‐area growth of high‐quality vertically aligned PtSe 2 , and its application to photodetectors based on PtSe 2 ‐GaAs heterojunctions which exhibit a broadband sensitivity to illumination ranging from deep ultraviolet to near‐infrared light, with a peak sensitivity in the region from 650 to 810 nm. The high‐performance broadband photodetector will develop the next‐generation 2D Group‐10 materials based optoelectronic devices.

Progress, challenges, and opportunities for HgCdTe infrared materials and detectors

Abstract: This article presents a review on the current status, challenges, and potential future development opportunities for HgCdTe infrared materials and detectortechnology. A brief history of HgCdTe infrared technology is firstly summarized and discussed, leading to the conclusion that HgCdTe-based infrared detectors will continue to be a core infrared technology with expanded capabilities in the future due to a unique combination of its favourable properties. Recent progress and the current status of HgCdTe infrared technology are reviewed, including material growth,device architecture, device processing, surface passivation, and focal plane array applications. The further development of infrared applications requires that future infrared detectors have the features of lower cost, smaller pixel size, larger array format size, higher operating temperature, and multi-band detection, which presents a number of serious challenges to current HgCdTe-based infrared technology. The primary challenges include well controlled p-type doping, lower cost, larger array format size, higher operating temperature, multi-band detection, and advanced plasma dry etching. Various new concepts and technologies are proposed and discussed that have the potential to overcome the existing primary challenges that are inhibiting the development of next generation HgCdTeinfrared detectortechnology.

Progress in Infrared Photodetectors Since 2000

Abstract: The first decade of the 21st-century has seen a rapid development in infrared photodetector technology. At the end of the last millennium there were two dominant IR systems, InSb- and HgCdTe-based detectors, which were well developed and available in commercial systems. While these two systems saw improvements over the last twelve years, their change has not nearly been as marked as that of the quantum-based detectors (i.e., QWIPs, QDIPs, DWELL-IPs, and SLS-based photodetectors). In this paper, we review the progress made in all of these systems over the last decade plus, compare the relative merits of the systems as they stand now, and discuss where some of the leading research groups in these fields are going to take these technologies in the years to come.

Quantum dots-in-a-well infrared photodetectors

Abstract: Novel InAs/InGaAs quantum dots-in-a-well (DWELL) infrared photodetectors are reviewed. These detectors, in which the active region consists of InAs quantum dots (QDs) embedded in an InGaAs quantum well, represent a hybrid between a conventional quantum well infrared photodetector (QWIP) and a QD infrared photodetector (QDIP). Like QDIPs, DWELL detectors display normal incidence operation without gratings or optocouplers while demonstrating reproducible 'dial-in recipes' for control over the operating wavelength, like QWIPs. Using femtosecond spectroscopy, long carrier lifetimes have been observed in DWELL heterostructures, suggesting their potential for high temperature operation. Moreover, DWELL detectors have also demonstrated bias-tunability and multicolour operation in the mid-wave infrared (3–5 µm), long-wave infrared (LWIR, 8–12 µm) and very long-wave infrared (>14 µm) regimes. We have recently developed LWIR 320 × 256 focal plane arrays operating at liquid nitrogen temperatures. One of the potential problems with these detectors is the low quantum efficiency, which translates into low responsivity and detectivity. Some solutions for mitigating these problems are suggested at the end of this paper.