M. A. Dem’yanenko

Application of uncooled microbolometer detector arrays for recording radiation of the terahertz spectral range

The mechanism of occurrence of sensitivity of microbolometer detector arrays based on vanadium oxide to terahertz radiation are analyzed. Experimental data are given showing the possibility of increasing the sensitivity of microbolometer detectors in the terahertz range by using an additional thin metal absorbing layer applied on the microbolometer membrane. A polarization dependence of the sensitivity of microbolometers in the terahertz and far infrared spectral ranges is found. It is shown that the sensitivity of microbolometers in the terahertz range is due to the absorption of radiation in the narrow metal runs placed on the support legs of the microbolometers and playing the role of an ohmic contact between the heat-sensitive layer and the processing curcuit.

Signal amplification under stochastic resonance in vanadium dioxide film

The phenomenon of stochastic resonance with an input signal gain of 1.6 times was observed in the planar structure that is connected in series with the loading resistor and has a VO2 conducting channel. It was shown that the signal-to-noise ratio transferring in the circuit can reach 250 times.

Infrared absorption in a multilayer bolometric structure with a thin metallic absorber

This paper presents relationships that make it possible to use the matrix method to calculate the reflectance, transmittance, and absorptance in a bolometric structure consisting of an arbitrary number of layers that include a metallic absorber and reflector. Analytic relationships are obtained that can be applied to actual bolometers—for example, fabricated on the basis of amorphous silicon, in which, besides a thin metallic absorber and reflector, there are two insulating layers (a high-resistance heat-sensitive layer and a thermally insulating layer). The relationships make it possible to take into account the imaginary component of the conduction of the metal layers and the gradual falloff of the radiation. This analysis, in particular, showed that taking into account an electron-relaxation time in the absorber equal to or greater than 10−14  s significantly alters not only the parameters of the bolometric structure but also the radiation frequency at which there is virtually complete absorption of the radiation.

Technological limitations in readout integrated circuits for infrared focal plane arrays based on quantum-well infrared photodetectors

This paper presents the physical and technical principles of readout integrated circuit (ROIC) for reading and preprocessing focal plane array signals in the infrared spectral range 8–14 μm. The noise equivalent temperature difference of long-wavelength infrared focal plane arrays based on ROIC with frame integration of signals of multilayer quantum well structures is evaluated. The influence of technological limitations in silicon readout circuits for photo signals on the performance of IR focal plane arrays is analyze for a wide range of parameters of QWIP -based focal plane arrays and CMOS technology design rules.

Multiphonon capture of charge carriers by deep-level centers in a depletion region of a semiconductor

Multiphonon field-assisted thermal capture of thermally equilibrium charge carriers by deep-level centers located in a depletion region of a semiconductor is analyzed. It is shown that, in the case of strong electron-phonon coupling (SEPC), the multiphonon capture with preliminary tunneling of an electron through a potential barrier in the depletion region occurs with a lower rate as compared to the direct multiphonon capture in the electrically neutral bulk of the semiconductor, whereas, in the case of weak electron-phonon coupling (WEPC), the capture rate in the depletion region of a semiconductor may exceed that in the electrically neutral bulk by several orders of magnitude. The results of experimental study of capture processes in AlGaAs doped with silicon indicate that electron-phonon coupling is strong in DX centers.

The nature of the deep levels responsible for photoelectric memory in GaAs/AlGaAs multilayer quantum-well structures

The electron capture parameters and photoionization cross section of the unintentional deep levels, which are responsible for photoelectrical memory in GaAs/AlGaAs multilayer quantum-well structures, have been found from an analysis of the kinetics of the excess current during and after optical illumination of these structures. The dependence of the photoionization cross section on the photon energy, the capture cross section, and the energy barrier for capture of an electron from the bottom of the conduction band indicate that the unintentional deep levels are DX centers formed by the silicon impurity. These DX centers probably appear during growth of the structures as a result of silicon diffusion from the quantum wells along as-grown defects.

Efficient Broadband Terahertz Radiation Detectors Based on Bolometers with a Thin Metal Absorber

The matrix method has been used to calculate the coefficients of absorption of terahertz radiation in conventional (with radiation incident from vacuum adjacent to the bolometer) and inverted (with radiation incident from the substrate on which the bolometer was fabricated) bolometric structures. Near-unity absorption coefficients were obtained when an additional cavity in the form of a gap between the bolometer and the input or output window was introduced. Conventional bolometers then became narrowband, while inverted-type devices remained broadband.

Optimizing the parameters of a system consisting of a photosensitive IR element based on multilayer structures with quantum wells and a silicon photoelectric multiplexer

This paper discusses the design and process principles involved in optimizing the noise-equivalent temperature difference of photodetectors based on multilayer structures with quantum wells in wide ranges of the structural and process limitations of silicon multiplexers, CMOS-technology design norms, and the parameters of photosensitive elements for the long-wavelength IR spectral region.

Development of analog-digital readout integrated circuits for infrared focal plane arrays

This paper describes the design of readout integrated circuits (ROICs) for hybrid infrared focal plane arrays (IR FPAs). This work contains the estimation of the noise equivalent temperature difference (NETD) of IR FPAs based on frame and row integration of pixel signals in the spectral ranges of 8 to 14 and 3 to 5 μm. This paper also describes the development of ROICs for IR FPAs created with the use of mercury—cadmium—telluride (MCT) photodiodes and quantum well infrared photodetectors (QWIPs). The designed ROICs ensure the use of matrix and linear photodetector chips, including those with increased dark currents, in order to produce IR FPAs with temperature resolution corresponding to the world level of array analogs.

Uncooled microbolometer mosaic focal plane arrays for the infrared and terahertz ranges

Mosaic focal plane arrays (MFPAs) have been designed, and a number of addressing schemes reducing the blind zone have been proposed. A precision technology for fabricating MFPAs with a total size of the blind zone of not more than 30 μm has been developed. Certain systemic issues of applying MFPAs are discussed. The designed 3072 × 576 uncooled microbolometer MFPAs based on 384 × 288 submodules with a pixel pitch of 17–51 μm provide ∼99% image conversion efficiency in the infrared range and those with a pixel pitch of 100 μm provide 100% image conversion efficiency in the terahertz range.