134 research outputs found
Technique for Magnetic Susceptibility Determination in the High Doped Semiconductors by Electron Spin Resonance
Method for determining the magnetic susceptibility in the high doped
semiconductors is considered. A procedure that is based on double integration
of the positive part of the derivative of the absorption line having a Dyson
shape and takes into account the depth of the skin layer is described. Analysis
is made for the example of arsenic doped germanium samples at a rather high
concentration corresponding to the insulator metal phase transition.Comment: Pages 13, figures 9, references 1
Out of equilibrium electronic transport properties of a misfit cobaltite thin film
We report on transport measurements in a thin film of the 2D misfit Cobaltite
. Dc magnetoresistance measurements obey the modified
variable range hopping law expected for a soft Coulomb gap. When the sample is
cooled down, we observe large telegraphic-like fluctuations. At low
temperature, these slow fluctuations have non Gaussian statistics, and are
stable under a large magnetic field. These results suggest that the low
temperature state is a glassy electronic state. Resistance relaxation and
memory effects of pure magnetic origin are also observed, but without aging
phenomena. This indicates that these magnetic effects are not glassy-like and
are not directly coupled to the electronic part.Comment: accepted in Phys Rev B, Brief report
Universal Crossover between Efros-Shklovskii and Mott Variable-Range-Hopping Regimes
A universal scaling function, describing the crossover between the Mott and
the Efros-Shklovskii hopping regimes, is derived, using the percolation picture
of transport in strongly localized systems. This function is agrees very well
with experimental data. Quantitative comparison with experiment allows for the
possible determination of the role played by polarons in the transport.Comment: 7 pages + 1 figure, Revte
Anderson Transitions
The physics of Anderson transitions between localized and metallic phases in
disordered systems is reviewed. The term ``Anderson transition'' is understood
in a broad sense, including both metal-insulator transitions and
quantum-Hall-type transitions between phases with localized states. The
emphasis is put on recent developments, which include: multifractality of
critical wave functions, criticality in the power-law random banded matrix
model, symmetry classification of disordered electronic systems, mechanisms of
criticality in quasi-one-dimensional and two-dimensional systems and survey of
corresponding critical theories, network models, and random Dirac Hamiltonians.
Analytical approaches are complemented by advanced numerical simulations.Comment: 63 pages, 39 figures, submitted to Rev. Mod. Phy
Кремниевая электронно-чувствительная pin-линейка, облучаемая с обратной стороны
Introduction. In recent decades, in the field of photoelectronics, special attention has been paid to the development of semiconductor matrix photodetectors. These detectors have become an effective alternative to existing television receiving systems. Among such devices, linear position-sensitive sensors are used in cases where the rapid registration of changes to the environment is required (for instance, high-speed locators for flying vehicles).Aim. To develop a strip of silicon pin-diodes as part of a hybrid IR-detector for effective registration of photoelectrons with time resolution less than 10 ns, as well as to model the key electro-physical characteristics of the strip.Materials and methods. In the device under development, the registration of photoelectrons is achieved by the presence of a near-surface field using p ++–p junction formed by diffusion of boron into the silicon with resistivity of 3 kΩ · cm. The pulling field is also formed in the space charge region between p ++ - and n ++ -regions. Diffusion of phosphorus was carried out to create the n ++ -region. Numerical calculations of potential distribution, concentration of free charge carriers and currents were carried out using software for 1D- and 2D-modelling (SimWin and TCAD Synopsys).Results. 2D-calculation of charge carrier concentration and potential distribution was performed. The study determined the minimum bias for the complete depletion of the i-layer, including that for longitudinal grooves of various depths. The strip was tested as part of a hybrid photoelectric device by irradiating light pulses from IR LED. When the voltage on the diodes was reached –270 V, the duration of the signal front on all channels was 5…9 ns.Conclusion. For use in IR-hybrid detectors, a strip of 12 silicon pin-diodes was developed with a sensitive element of 24 × 0.2 mm in dimension. The study of pulse characteristics showed that the necessary duration of the front signal on all channels was achieved without thinning thus satisfying the requirements for high-speed position-sensitive sensor of the infrared radiation.Введение. В последние десятилетия в фотоэлектронике особое внимание уделяется разработке полупроводниковых матричных фотоприемных устройств, которые фактически стали эффективной альтернативой существующим аналоговым телевизионным приемным системам. Среди таких устройств линейные позиционно-чувствительные датчики применяются для регистрации быстрых изменений в окружающей обстановке и их последующей обработки (например, быстродействующие локаторы летательных аппаратов).Цель работы. Создание линейки кремниевых pin-диодов для использования в составе гибридного детектора ИК-излучения с целью регистрации фотоэлектронов с временны́м разрешением лучше 10 нс. Моделирование основных электрофизических характеристик линейки.Материалы и методы. В разрабатываемом приборе регистрация фотоэлектронов обеспечивается за счет наличия приповерхностного поля при использовании p ++–p-перехода, сформированного диффузией бора в кремний с удельным сопротивлением 3 кОм · см. Тянущее поле, в свою очередь, также формируется в области объемного заряда между p ++ - и n ++ -областями. Для создания n ++ -области проводилась диффузия фосфора. Численные расчеты распределения потенциала, концентрации свободных носителей заряда и токов проводились в программных пакетах одномерного (SimWin) и двумерного (TCAD Synopsys) моделирования.Результаты. Проведен двумерный расчет распределения концентрации свободных носителей заряда и потенциала в исследуемой pin-структуре. Определены минимальные напряжения, обеспечивающие полное обеднение i-слоя, в том числе для случая продольной канавки различной глубины. Линейка тестировалась в составе гибридного фотоэлектронного прибора облучением световыми импульсами от ИК-светодиода. При напряжении на диодах линейки –270 В достигнута длительность фронта сигнала на всех каналах 5...9 нс.Заключение. Для гибридного детектора ИК-излучения разработана линейка из 12 кремниевых pin-диодов, с размерами чувствительной области элемента 24 × 0.2 мм. По результатам исследований импульсной характеристики показано, что без операции утонения достигнута длительность фронта сигнала на всех каналах, удовлетворяющая требованиям к быстродействующему позиционно-чувствительному датчику ИК-излучения
Dopant-induced crossover from 1D to 3D charge transport in conjugated polymers
The interplay between inter- and intra-chain charge transport in bulk
polythiophene in the hopping regime has been clarified by studying the
conductivity as a function of frequency (up to 3 THz), temperature and doping
level. We present a model which quantitatively explains the observed crossover
from quasi-one-dimensional transport to three-dimensional hopping conduction
with increasing doping level. At high frequencies the conductivity is dominated
by charge transport on one-dimensional conducting chains.Comment: 4 pages, 2 figure
Transition of Carrier Transport Behaviors with Temperature in Phosphorus-Doped Si Nanocrystals/SiO2 Multilayers
Hysteresis of magnetoresistance in neutron-transmutation-doped Ge in the region of hopping transport over the Coulomb-gap states
Operational voltage of silicon heavily irradiated strip detectors utilizing avalanche multiplication effect
Recent results on the collected charge in heavily irradiated Si strip detectors developed by RD50 collaboration for the high luminosity operation of the LHC (sLHC) showed a significant enhancement if the detectors were operated at a bias voltage beyond 1000 V. To explain these results, a physical model based on carrier avalanche multiplication in high electric fields near a n-p junction was developed at the Ioffe Physical-Technical Institute. This study represents an extension of the model, whose goal is finding the detector bias voltage and the other operating conditions which lead to such charge enhancement. The electric field distribution and collected charge in heavily irradiated Si strip detectors are calculated at different conditions: bias voltage, temperature, radiation fluence and strip detector geometry. It is demonstrated that: a) the minimum operational voltage, which initiates the avalanche process, depends on the fluence (being 500 V and 1500 V for LHC and sLHC fluence range, respectively), b) in avalanche multiplication mode the electric field near the n-strips is stabilized via potential redistribution inside the detector and formation of a pronounced DP electric field profile and is about 300 kV/cm, and c) the model predicts that the maximum collected charge in detectors irradiated to \rm{n}_{eq}cm^{-2}Q_c$
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