V. V. Vasil'ev

320×256 photodetector arrays with a built-in short-wavelength cutoff filter

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.

Investigating processes for forming an infrared CdHgTe-based photodetector in a monolithic version

This paper discusses the results of investigations of processes for forming monolithic integrated cadmium-mercury telluride (CdHgTe)-based IR arrays and their parameters. The processes for growing CdHgTe heteroepitaxial layers (HELs) by molecular-beam epitaxy (MBE) in the cells of a silicon multiplexer have been studied, as well as for forming an n-p junction and contact compounds. For the selective growth of CdHgTe MBE HELs, regimes have been determined for preparing a silicon surface in dielectric windows with dimensions from 30×30to100×100μm. Selective layers of CdHgTe (8μm)/CdTe(5-7μm)/ZnTe(0.02μm) have been grown on Si (310). Ion implantation of boron into selective p-type layers has been used to form n-p junctions. Measurements showed that the parameter R0A is 1.25×105Ωcm2 for the spectral range 3-5μm. A monolithic linear array of format 1×32, based on a CdHgTe MBE HEL, has been fabricated by growth in the cells of a silicon multiplexer.

Linear 288×4-format photodetector with a bidirectional time-delay-and-storage regime

Infrared n-p-photodiode photodetectors based on a hybrid assembly of photosensitive elements of format 288×4 with a 56×43-μm step, made from mercury-cadmium telluride heteroepitaxial structures obtained by molecular-beam epitaxy, have been developed, fabricated, and investigated for the 8–12-μm spectral range, along with silicon multiplexers with bidirectional scanning and internal time delay and storage of the signal. The 288×4-format linear photodetector has the following mean values of voltage sensitivity, detectivity, and NETD at the maximum sensitivity: (1–3)×108V∕W, (1.5–2.0)×1011cmHz1∕2W−1, and 9mK, respectively. There are no defective channels.

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.

HgCdTe nanostructures on GaAs and Si substrate for IR and THz radiation detecting

All-round studies of heteroepitaxial HgCdTe nanostructures (NS) growth on GaAs and Si substrates by molecular beam epitaxy have been carried out. In case of Si substrate HgCdTe NSs is very perspectives for IR detectors because of equal thermal expention coefficient with silicon read-out circuits. The problems of HgCdTe conjugations with Si at epitaxy connected with large differences in lattice mismatch and differences in chemical bonding that leads to antiphased domains. We found that the precise formation of transition layer (2 nm in thickness between Si substrates and first ZnTe buffer layer leads to growth HgCdTe NSs without antiphrasis domains. V-defects and etch pits densities are equal to 103 cm−2 and 107 cm−2 respectively. The HgCdTe/Si were used for fabrication photovoltaic 640×512 MWIR focal plane arrays. The operability for λ1/2 = 4.2 μm (77K) was over 97%. The response (Sv) and NETD were as 1,5 × 109 V/W and less 20 mK respectively. We developed the precise growth of symmetric and antisymmetric HgTe QW. We found the following effects: the presence 2D electron gas with high mobilities over 5×105 cm/V×s in doped HgTe QW, the presence @D holes and electrons in undoped HgTe QW and high sensitivity to linear and circular polarized IR and THz radiation in 6 – 400 μm region.

Comparison of the current characteristics of photodiodes formed on CdHgTe films grown by molecular-beam and liquid-phase epitaxy for the 8-12-μm spectral range

This paper presents a comparison of the dark currents and differential resistance of photodiodes, obtained using p-type cadmium-mercury telluride (CdHgTe) layers doped with boron ions, grown by molecular-beam epitaxy (MBE) and liquid-phase epitaxy (LPE). The volt-ampere responses for diodes on CdHgTe layers with composition x=0.215, grown by MBE and LPE (x≈0.222) are characterized by various saturation currents (reverse bias −0.25V) of 1-2 and 5-10nA, even though the band gap is greater for the latter. In this case, the maximum differential resistance is 4×109 and 5×107Ω for diodes based on MBE and LPE layers, respectively. The experimental data are compared with the calculated values. Numerical modelling showed that, for MBE structures with low biases, the dark current is limited by the diffusion current and by the Shockley-Read-Hall current outside the n-p junction, whereas, in LPE structures, there is a substantial contribution of currents through traps in the depletion region.

Infrared photodetector modules based on variband layers of HgCdTe and on structures with GaAs/AlGaAs quantum wells

A process has been developed for producing linear and two-dimensional array-type photodetector modules (PDMs), including the fabrication of photodetector structures based on heteroepitaxial layers of CdxHg1−xTe and GaAs/AlGaAs grown by molecular-beam epitaxy, fabrication of two-dimensional and linear arrays of silicon multiplexers, and hybrid assembly of PDMs consisting of a photodetector structure and a multiplexer by means of indium microposts. The photoelectric parameters are given for two-dimensional and linear array-type PDMs based on photodiodes for the mid-IR (3-5.5 µm) and far-IR (8-12 µm) regions, operating at temperatures of 78-80 K and 200-220 K.

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.