A. O. Suslyakov

Infrared focal plane assemblies based on HgCdTe/Si(310) heterostructure

It is demonstrated for the first time that high-performance scanning infrared (IR) focal plane assemblies of the 288 × 4 format for long-wavelength (8–12 μm) IR spectral range can be created based on a CdxHg1 − xTe/Si(310) heterostructure.

HgCdTe heterostructures grown by MBE on Si(310) substrates: structural and electrophysical properties

Molecular beam epitaxy has been used for the growth of Hg1-xCdxTe layers (x = 0.30 - 0.34) on Si(310) substrates. The grown structures were characterized by Hall measurements for carrier density and mobility. The densities of stacking faults, threading dislocations, antiphase boundaries and macroscopic V-defects were determined by selective chemical etching. The 128 x 128 photodiode array with wavelength cut-off λ1/2(77K) = 4.07 μm was fabricated with good photoelectric parameters.

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

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.

Study of the effect of graded gap epilayers on the performance of CdxHg1−xTe photodiodes

The characteristics of the photodiodes based on CdxHg1−xTe solid solutions with graded gap layers were calculated in the context of a one-dimensional diffusion-drift model. The parameters of the photodiodes were shown to be improved when the p-n junction was located in the near-surface graded gap region rather than in the central homogeneous section of the structure. The photodiodes with the n-type layer adjacent to the substrate were found to offer an advantage over the diodes with the p-layer close to the substrate in the case of illumination from the substrate side.

LWIR Photodiodes and Focal Plane Arrays Based on Novel HgCdTe/CdZnTe/GaAs Heterostructures Grown by MBE Technique

Thermal imagers based on the photo detectors for infrared (IR) wavelength range of 3–12 μm are required for applications both in the military equipment for systems of night vision, detection and guidance as well as in the national economy for the medical, agricultural, chemical, metallurgical, fuel industries and others. Nowadays, the leading place among ma‐ terials for the production of IR photo detectors is occupied by mercury–cadmium–telluride (MCT) solid solutions. This fact is due to the physical properties of these solutions (high speed, the possibility of varying an MCT band gap within a wide range, and high quantum efficiency in the range of overlapping wavelengths). For the last 25 years, the technology of MCT production has been developed intensively, which has made it possible to pass from manufacturing bulk single crystals of relatively small diameters (less than 10 mm) to epilay‐ ers on large in diameter substrates (up to 150 mm). The MCT epilayers on large-diameter substrates are necessary for the production of IR PD arrays with a large number of elements for enhancing the production efficiency and reducing the cost of devices. According to this, stringent requirements are imposed on the epitaxial technologies of producing such an MCT material. They include a high structural quality and uniformity of photoelectric characteris‐ tics over the entire area. MCT layers on alternative substrates primarily due to its low growth temperatures (~180 oC), which prevents the diffusion of impurities from the sub‐ strate and reduces the background doping with these impurities. The great successes had

MCT infrared photodiodes on the basis of graded gap P-p heterojunction grown by MBE HgCdTe epilayers on GaAs

The measurement signal (S) to noise (N) ratio (S/N) of novel 128×128 FPA in temperature range 77 -130K was carried out. FPA for spectral range 8-12 μm was fabricated by B+ implantation process into graded MCT P-p heterojunction with potential barrier. MCT P-p heterojunction with specific MCT composition throughout the thickness was grown by MBE on GaAs substrate by ellipsometric control in situ. The potential barrier was determined by the difference of MCT composition at absorber and p-n junction location layers and equal to ΔXCdTe = 0,025. It was shown that based on P-p heterojunction FPA operated temperature and wavelength increases over routine one without P-p heterojunction. Keywords: graded gap layers, heterojunction, MCT, photodiodes, FPA.

Planar photodiodes based on p-HgCdTe (x = 0.22) epilayers grown by molecular beam epitaxy

This paper reports on the realization of small area long-wavelength infrared (LWIR) photodiodes based on CdHgTe films grown by molecular beam epitaxy (MBE). The composition of the ternary compound is controlled in situ by a single-wave ellipsometer that offers the possibility to grow epilayers with a desirable composition profile across the film thickness. Photodiodes have a vertical configuration and have been fabricated using planar technology by annealing under an anodic oxide film.