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)

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HgCdTe infrared detector material: history, status and outlook

We demonstrate the growth of potential barriers, wells and periodic nanostructures on the basis of Hg1-xCdxTe by molecular beam epitaxy. In situ single wavelength ellipsometry is used for control of thickness and variation of Hg1-xCdxTe composition. The behavior of ellipsometric parameters measured during the growth of potential barriers, wells and periodic structures are in good agreement with the numerical calculated of variation of ellipsometric parameters ψ and Δ. The thickness and composition of Hg1-xCdxTe nanolayers were determined from comparison of experimental and calculated ψ and Δ. The accuracy of nanolayer thickness determination reaches the value of 0.1 nm and composition ±0.002 mole fraction.

Growth of Hg1-xCdxTe nanostructures by molecular beam epitaxy with ellipsometric control

We report on stimulated emission at wavelengths up to 19.5 μm from HgTe/HgCdTe quantum well heterostructures with wide‐gap HgCdTe dielectric waveguide, grown by molecular beam epitaxy on GaAs(013) substrates. The mitigation of Auger processes in structures under study is exemplified, and the promising routes towards the 20–50 μm wavelength range, where HgCdTe lasers may be competitive to the prominent emitters, are discussed.

Stimulated emission from HgCdTe quantum well heterostructures at wavelengths up to 19.5 μm

We report room-temperature operation of 1 × 1 cm2 infrared photoconductive photodetectors based on silicon supersaturated with titanium. We have fabricated these Si-based infrared photodetectors devices by means of ion implantation followed by a pulsed laser melting process. A high sub-band gap responsivity of 34 mV W−1 has been obtained operating at the useful telecommunication applications wavelength of 1.55 μm (0.8 eV). The sub-band gap responsivity shows a cut-off frequency as high as 1.9 kHz. These Si-based devices exhibit a non-previous reported specific detectivity of 1.7 × 104 cm Hz1/2 W−1 at 660 Hz, under a 1.55 μm wavelength light. This work shows the potential of Ti supersaturated Si as a fully CMOS-compatible material for the infrared photodetection technology.

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Room-temperature operation of a titanium supersaturated silicon-based infrared photodetector

We report a fast, room temperature detection scheme for the polarization ellipticity of laser radiation, with a bandwidth that stretches from the infrared to the terahertz range. The device consists of two elements, one in front of the other, that detect the polarization ellipticity and the azimuthal angle of the ellipse. The elements, respectively, utilize the circular photogalvanic effect in a narrow gap semiconductor and the linear photogalvanic effect in a bulk piezoelectric semiconductor. For the former we characterized both a HgTe quantum well and bulk Te, and for the latter, bulk GaAs. In contrast with optical methods we propose is an easy to handle all-electric approach, which is demonstrated by applying a large number of different lasers from low power, continuous wave systems to high power, pulsed sources.

http://www.physik.uni-regensburg.de/forschung/ganichev/reprints/JApplPhys_105_013106.pdf

Fast detector of the ellipticity of infrared and terahertz radiation based on HgTe quantum well structures

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.

HgCdTe epilayers on GaAs: growth and devices

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.

Focal plane arrays based on HgCdTe epitaxial layers MBE-grown on GaAs substrates

The molecular beam epitaxy (MBE) set-up with analytical control equipment of growth process was designed and fabricated for growing A2B6 compounds including the mercury-containing ones. A technology was elaborated for growing mercury-cadmium-telluride (MCT) solid solution heteroepitaxial structures (HS) by molecular beam epitaxy (MBE) method with a given variation of MCT composition throughout the thickness. HS's MCT MBE on CdZnTe/GaAs substrate with different variation composition in layers at MCT film interfaces were designing and growing. These structures were used for manufacture of high quality single, linear and array photoconductors (PC) and photodiodes (PD) operating at 77 K and 200 - 250 K temperature in the wavelength range of 3 - 5 micrometer and 8 - 12 micrometer, up and over 20 micrometer. Widegap layers at MCT film interfaces are used as passivating coating. Narrowgap layer at MCT film/CdZnTe buffer layers interface is used for decrease of PD series resistance. For decrease of dark currents of photodiodes array operating at 200 K HS MCT MBE were used with special composition distribution of composition throughout the thickness.

MCT heterostructure design and growth by MBE for IR devices

The molecular beam epitaxy (MBE) set-up with analytical control equipment of growth process was designed and fabricated for growing A 2 B 6 compounds including the mercury-containing ones. A technology was elaborated for growing mercury-cadmium-telluride (MCT) solid solution heteroepitaxial structures (HS) by molecular beam epitaxy (MBE) method with a given variation of MCT composition throughout the thickness. HS's MCT MBE on CdZnTe/GaAs substrate with different variation composition in layers at MCT film interfaces were designing and growing. These structures were used for manufacture of high quality single, linear and array photoconductors (PC) and photodiodes (PD) operating at 77 K and 200-250 K temperature in the wavelength range of 3-5 μm and 8-12 μm, up and over 20 μm. Widegap layers at MCT film interfaces are used as passivating coating. Narrowgap layer at MCT film/CdZnTe buffer layers interface is used for decrease of PD series resistance. For decrease of dark currents of photodiodes array operating at 200 K HS MCT MBE were used with special composition distribution of composition throughout the thickness.

MCT heterostructures designing and growing by MBE for IR devices

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.

A. O. Suslyakov

Papers

HgCdTe epilayers on GaAs: growth and devices

Focal plane arrays based on HgCdTe epitaxial layers MBE-grown on GaAs substrates

MCT heterostructure design and growth by MBE for IR devices

MCT heterostructures designing and growing by MBE for IR devices

The 4×288 linear FPA on the heteroepitaxial Hg 1-x Cd x Te base