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Terahertz Photoconductivity in Graphene in a Magnetic Field
摘要： The terahertz photoconductivity in epitaxial graphene grown on SiC substrates is investigated in a magnetic field. The magnetic-field dependence of the photoresponse signal amplitude is examined at different electron densities, bias currents, and terahertz radiation intensities. The experimental results are explained well by a photoconductivity mechanism based on the heating of electrons by terahertz radiation. A strong increase in the photoconductivity signal with increasing magnetic field caused by an increase in the relaxation time due to the suppression of electron-electron scattering is observed.
关键词： terahertz radiation,photoconductivity,magnetic field,graphene
更新于2025-09-23 15:21:01
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Nonlinear Optical Absorption in GaSe upon Laser Excitation
摘要： The nonlinear absorption in GaSe crystals at high optical excitation levels is experimentally studied. A Nd:YAG laser (first and second harmonics, 1064 and 532 nm) and a liquid laser (tuning range 594–643 nm) were used as excitation sources. It is shown that the features observed in the exciton resonance region of the absorption, luminescence, and photoconductivity spectra of GaSe crystals at high optical excitation levels can be explained by exciton–exciton interaction and Coulomb interaction screening by free carriers.
关键词： GaSe,photoconductivity,nonlinear absorption,luminescence
更新于2025-09-23 15:21:01
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Mechanism of leakage current increase in p-GaN gate AlGaN/GaN power devices induced by ON-state gate bias
摘要： An increase in OFF-state leakage current in p-GaN gate AlGaN/GaN high-electron-mobility transistors (HEMTs), induced by ON-state gate bias, was observed and reported in this paper. Higher OFF-state leakage current was observed with higher gate bias voltage and longer bias duration. We propose that the initial increase in OFF-state leakage current and its subsequent decay with time are due to persistent photoconductivity effects in GaN induced by hole injection and electroluminescence during the ON-state gate bias. At room temperature, it took more than 20 s for the increased leakage current to reduce to its equilibrium level in the dark. The related physical mechanisms underlying this phenomenon in the p-GaN gate HEMT structure are also proposed.
关键词： p-GaN gate,AlGaN/GaN HEMTs,persistent photoconductivity,leakage current,electroluminescence
更新于2025-09-23 15:21:01
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[IEEE 2018 43rd International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz2018) - Nagoya, Japan (2018.9.9-2018.9.14)] 2018 43rd International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz) - Effect of Magnetic Field on Terahertz Photoconductivity in Hg<inf>l-x</inf>Cd<inf>x</inf>Te-Based Structures
摘要： In this paper, we show that the positive terahertz photoconductivity in Hg1-xCdxTe solid solutions being in a topological phase (x < 0.16) strongly depends on the combination of both the external magnetic field direction and the potential probe position. The asymmetry in the photoresponse in the magnetic field may be due to the spin-related features of the carriers excited.
关键词： topological phase,spin-related features,Hg1-xCdxTe,terahertz photoconductivity,magnetic field
更新于2025-09-23 15:21:01
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Influence of Film Morphology on Transient Photocurrent Pulse Shape in Organic Thin Films: A Monte Carlo Study
摘要： The in?uence of ?lm morphology on the broadening of the time-of-?ight transient photo-current pulse is investigated using Monte Carlo simulation. Simulation of the time-of-?ight transient photo-current pulse shape is carried out for homogeneous and inhomogeneous organic thin ?lms by varying the overall energetic disorder. In homogeneous system, the value of the tail broadening parameter (W) of the photocurrent pulse is found to decrease upon decreasing the energetic disorder, which can be attributed to the variation in the non-thermal ?eld assisted diffusion. Interestingly, in the case of inhomogeneous system, upon decreasing the overall energetic disorder of the system the value of W initially attains a maximum value before it starts decreasing. This observation is explained in terms of the morphology dependent carrier diffusion. This study asserts the importance of the in?uence of the morphology dependent carrier diffusion on the charge transport in disordered systems and the related experimental measurements.
关键词： Polycrystalline organic thin ?lms,Charge transport,Tail broadening,Diffusion,Time of ?ight photoconductivity,Film Morphology
更新于2025-09-23 15:21:01
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A Preamplifier for a CdHgTe Photodetector
摘要： A preamplifier for operation with an HgCdTe-based nitrogen-cooled IR photodetector (600 nm–15 μ m) is described. The preamplifier operates in the photoconductivity mode. The use of modern microcircuits made it possible to increase the bandwidth of the response to 2 MHz at a noise level of 0.5 nV/Hz1/2, which is close to the fundamental limit that is specified by the resistance of the photosensitive element. The preamplifier was used in an aperture-free scanning near-field optical microscope.
关键词： HgCdTe,IR photodetector,scanning near-field optical microscope,photoconductivity,preamplifier
更新于2025-09-23 15:19:57
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SnSe2 Field-Effect Transistor with High On/Off Ratio and Polarity-Switchable Photoconductivity
摘要： SnSe2 field-effect transistor was fabricated based on exfoliated few-layered SnSe2 flake, and its electrical and photoelectric properties have been investigated in detail. With the help of a drop of de-ionized (DI) water, the SnSe2 FET can achieve an on/off ratio as high as ~ 104 within 1 V bias, which is ever extremely difficult for SnSe2 due to its ultrahigh carrier density (1018/cm3). Moreover, the subthreshold swing and mobility are both improved to ～ 62 mV/decade and ~ 127 cm2 V?1 s?1 at 300 K, which results from the efficient screening by the liquid dielectric gate. Interestingly, the SnSe2 FET exhibits a gate bias-dependent photoconductivity, in which a competition between the carrier concentration and the mobility under illumination plays a key role in determining the polarity of photoconductivity.
关键词： Photoconductivity,SnSe2,Field-effect transistor,On/off ratio
更新于2025-09-19 17:15:36
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Investigation of Conductivity Characteristics of Zn-In-Se Thin Films
摘要： Zn-In-Se thin films were fabricated on the ultrasonically cleaned glass substrates masked with clover-shaped geometry by thermal evaporation of its elemental sources. Temperature dependent conductivity characteristics of the films were investigated under dark and illuminated conditions. The semiconductor type of the films was found as n-type by thermal probe test. According to the van der Pauw technique, the dark electrical conductivity analyses showed that the variations of conductivity of unannealed and annealed at 300°C samples are in exponential dependence of temperature. These conductivity profiles were found to be dominated by the thermionic emission at high temperature region whereas their behaviors at low temperatures were modeled by hopping theory. On the contrary, as a result of the further annealing temperatures, the surface of the samples showed semi-metallic characteristics with deviating from expected Arrhenius behavior. In addition, the temperature dependent photoconductivity of the films was analyzed under different illumination intensities and the results were explained by the supra-linear characteristic based on the two-center recombination model.
关键词： Photoconductivity,Thin film,Annealing,Transport properties
更新于2025-09-19 17:15:36
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Sensors, Circuits and Instrumentation Systems (2018) || Investigation of Optoelectronic Properties of Amorphous Silicon Germanium Photodetectors
摘要： Cost consideration of the development of electronic devices is one of prime importance. One simple approach to lower the cost of production of photovoltaic and detectors is by using low cost materials such as amorphous silicon and germanium. These two semiconductors have different optoelectronic properties, such as energy gap, photoconductivity and absorption coefficient. The use of an alloy from the mixing of silicon with certain percentages of germanium would produce photodetectors with improved electronic characteristics and photoconductivity. A number of a-SiGe alloy thin films with different quantities of germanium have been fabricated using thermal vacuum evaporation technique. Conduction mechanism and activation energy of the prepared samples had been calculated and analyzed. The I–V characteristics, the photogenerated current and detectivity of these samples are subjected to measurement and discussion. Hall measurements are also conducted so to calculate the Hall I–V characteristics, Hall mobility, carrier concentration and type identification of the samples.
关键词： Amorphous silicon germanium photodetector,photoconductivity,detectivity,Hall measurements,activation energy,conduction mechanism
更新于2025-09-16 10:30:52
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Wavelength and Constant Magnetic field Dependence of the Steady-state Photoconductivity of a Bifacial Silicon Solar Cell
摘要： In this work, a theoretical study on the photoconductivity of a bifacial silicon solar cell under monochromatic illumination and constant magnetic field is presented. Analytical expression of the photoconductivity is established according to base depth, illumination wavelength, junction recombination velocity and magnetic field value. The photoconductivity profile versus wavelength shows two energy absorption peaks corresponding to specific wavelengths. Based on a linear model of the photoconductivity versus junction recombination velocity, in a given interval, we determine an equivalent capacitance which depends on both wavelength and magnetic field.
关键词： Capacitance,Recombination velocity,Wavelength,Photoconductivity,Magnetic field
更新于2025-09-16 10:30:52