Calculation of thermal parameters of SiGe microbolometers

The thermal parameters of a SiGe microbolometer were calculated using numerical modeling. The calculated thermal conduction and thermal response time are in good agreement with the values found experimentally and range between 2x10$^-7$ and 7x10$^-8$ W/K and 1.5 and 4.5 ms, respectively. High sensitivity of microbolometer is achieved due to optimization of the thermal response time and thermal conduction by fitting the geometry of supporting heat-removing legs or by selection of a suitable material providing boundary thermal resistance higher than 8x10$^-3$ cm$^2$K/W at the SiGe interface.Comment: 11 pages, 6 figure

Impact of the graded-gap layer on the admittance of MIS structures based on MBE-grown n-Hg1-xCdxTe (x = 0.22-0.23) with the Al2O3 insulator

The impact of the presence of the near-surface graded-gap layers with an increased content of CdTe on the admittance of MIS structures based on MBE-grown n-Hg1–xCdxTe (x = 0.22–0.23) with the Al2O3 insulating coating has been experimentally studied. It has been shown that the structures with a gradedgap layer are characterized by a deeper and wider capacitance dip in the low-frequency capacitance–voltage (CV) characteristic and by higher values of the differential resistance of the space-charge region than the structures without such a layer. It has been found that the main features of the hysteresis of capacitance dependences typical of the graded-gap structures with SiO2/Si3N4 are also characteristic of the MIS structures with the Al2O3 insulator. The factors that cause an increase in the CV characteristic hysteresis upon formation of the graded-gap layer in structures with SiO2/Si3N4 or Al2O3 are still debatable, although it may be assumed that oxygen plays a certain role in formation of this hysteresis

Admittance of MIS structures based on graded-gap MBE HgCdTe with Al2O3 insulator

The paper presents the results of studies of the admittance of MIS structures based on heteroepitaxial MBE n (p)-Hg0.78Cd0.22Te with insulator coating SiO2/Si3N4 and Al2O3 in the test signal frequency range 10 kHz-1 MHz at temperatures ranging from 8 to 220 K. The main parameters of MIS structures with different insulators were determined. MIS structures with Al2O3 have a large enough insulator capacitance (compared to SiO2/Si3N4), a significant modulation capacitance on the CV characteristics, high dielectric strength and low values of the flat-band voltage. The effective charge density found from the value of the flat-band voltage and slow interface trap density for structures with Al2O3 comparable with the corresponding densities for structures with SiO2/Si3N4

ЭЛЕКТРОФИЗИЧЕСКИЕ И ФОТОЭЛЕКТРИЧЕСКИЕ ХАРАКТЕРИСТИКИ МДП–СТРУКТУР НА ОСНОВЕ ГЕТЕРОЭПИТАКСИАЛЬНОГО HgCdTe, ПОЛУЧЕННОГО МЕТОДОМ МОЛЕКУЛЯРНО–ЛУЧЕВОЙ ЭПИТАКСИИ, C НЕОДНОРОДНЫМ РАСПРЕДЕЛЕНИЕМ СОСТАВА

The electro-physical and photoelectrical properties of MIS structures based on HgCdTe MBE with non-uniform distribution of composition were experimentally investigated. It is shown that near-surface graded-gap layers with elevated composition strongly affect on dependencies of the capacitance and the photo-emf versus the bias voltage and frequency for the MIS structures based on n-Hg1-xCdxTe (x = 0.21—0.23). The characteristics of MIS structures based on n-Hg0.7Cd0.3Te with periodically located regions with high composition were investigated and it is shown that these regions are most strongly affect the characteristics of MIS structures when their location near the boundary of the insulator−semiconductor. The electrical properties of MIS structures based on n-Hg1-xCdxTe (x = 0.62—0.73) with region with lower composition were experimentally studied.Экспериментально исследованы электрофизические и фотоэлектрические свойства МДП-структур на основе HgCdTe, полученного методом молекулярно-лучевой эпитаксии, с неоднородным распределением состава. Показано, что для МДП-структур на основе n-Hg1-xCdxTe (x = 0,21-0,23) приповерхностные варизонные слои с увеличенным содержанием СdTe на поверхности сильно влияют на зависимости емкости и фотоЭДС от напряжения смещения и частоты. Исследованы характеристики МДП-структур на основе n-Hg0,7Cd0,3Te с периодически расположенными областями резко повышенного содержания CdTe барьерного типа и показано, что эти области оказывают влияние на характеристики МДП-структур при их расположении вблизи границы раздела диэлектрик—полупроводник. Экспериментально изучены электрические свойства МДП-структур на основе n-Hg1-xCdxTe (x = 0,62-0,73) с областями пониженного содержания CdTe в приповерхностной области типа потенциальных ям

Influence of As+ Ion implantation on properties of MBE HgCdTe near-surface layer characterized by metal–insulator–semiconductor techniques

The effect of As+ ion implantation on the electrical properties of the near-surface layer of n-HgCdTe films grown by molecular beam epitaxy (MBE) on Si (310) substrates was experimentally studied. A specific feature of MBE n-Hg0.78Cd0.22Te films is the presence of near-surface graded-gap layers with a high CdTe content, formed during epitaxial growth. The properties of as-grown films and films after As+ ion implantation with ion energy of 200 keV and fluence of 1014 cm−2 were studied. Post-implantation activation annealing was not performed. Test metal–insulator–semiconductor (MIS) structures were created based on as-grown and as-implanted samples by plasma-enhanced atomic layer deposition of Al2O3 insulator films. The admittance of the fabricated MIS structures was measured over a wide range of frequencies and temperatures. When determining the parameters of MIS structures, we used techniques that take into account the presence of near-surface graded-gap layers and series resistance of the HgCdTe film bulk, as well as the high density of slow surface states. It was found that, in as-implanted samples, the donor center concentration in the near-surface layer exceeds 1017 cm−3 and increases with distance from the HgCdTe-Al2O3 interface (at least up to 90 nm). After implantation, the conductivity of MBE HgCdTe film bulk increases markedly. It was shown that, for as-implanted samples, the generation rate of minority charge carriers in the MBE HgCdTe surface layer is significantly reduced, which indicates the appearance of a low defect layer with a thickness of at least 90 nm

The spin label amino acid TOAC and its uses in studies of peptides: chemical, physicochemical, spectroscopic, and conformational aspects

We review work on the paramagnetic amino acid 2,2,6,6-tetramethyl-N-oxyl-4-amino-4-carboxylic acid, TOAC, and its applications in studies of peptides and peptide synthesis. TOAC was the first spin label probe incorporated in peptides by means of a peptide bond. In view of the rigid character of this cyclic molecule and its attachment to the peptide backbone via a peptide bond, TOAC incorporation has been very useful to analyze backbone dynamics and peptide secondary structure. Many of these studies were performed making use of EPR spectroscopy, but other physical techniques, such as X-ray crystallography, CD, fluorescence, NMR, and FT-IR, have been employed. The use of double-labeled synthetic peptides has allowed the investigation of their secondary structure. A large number of studies have focused on the interaction of peptides, both synthetic and biologically active, with membranes. In the latter case, work has been reported on ligands and fragments of GPCR, host defense peptides, phospholamban, and β-amyloid. EPR studies of macroscopically aligned samples have provided information on the orientation of peptides in membranes. More recent studies have focused on peptide–protein and peptide–nucleic acid interactions. Moreover, TOAC has been shown to be a valuable probe for paramagnetic relaxation enhancement NMR studies of the interaction of labeled peptides with proteins. The growth of the number of TOAC-related publications suggests that this unnatural amino acid will find increasing applications in the future

Admittance studies of modification of HgCdTe surface properties with ion implantation and thermal annealing

Metal–insulator–semiconductor (MIS) structures based on HgCdTe were fabricated after various stages of p