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Preparation and some properties of Mg <sub/>2</sub> Si <sub/>0.53</sub> Ge <sub/>0.47</sub> single crystal and Mg <sub/>2</sub> Si <sub/>0.53</sub> Ge <sub/>0.47</sub> pn-junction diode
摘要： This paper reports the results on fabrication methodology and photoresponse characteristics of Mg2Si0.53Ge0.47 pn-junction photodiode. At first, we have grown a Mg2Si0.53Ge0.47 single crystal with the Vertical Bridgman growth process. The grown crystal was characterized structurally and electrically by XRD, Laue, and Hall Effect measurements. XRD revealed the single-phase composition, Mg2Si0.53Ge0.47, of the grown crystal ingot. The clear Laue symmetrical diffraction pattern showed the single crystalline nature of the grown crystal. The Hall Effect measurement revealed the n-type conduction and the moderate Hall mobility (258 cm2/Vs), electrical resistivity (6.03E-02 ?. cm), and carrier density (4.02E+17 cm-3) of the grown crystal. Such carrier density is low enough to allow depletion region formation in case of pn-junction diodes. In that sense, we have made up for the first time Mg2Si0.53Ge0.47 pn-junction photodiode by thermal diffusion of a thin Ag layer into n-Mg2Si0.53Ge0.47 substrate. The fabricated diode had an obvious rectification behavior and demonstrated a clear zero-biased photoresponse in the wavelength range from 0.95 to 1.85 μm, indicating its prominence for IR sensation in that wavelength domain.
关键词： IR sensation,photoresponse,pn-junction diode,Mg2Si0.53Ge0.47,single crystal
更新于2025-09-10 09:29:36
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[IEEE 2018 Conference on Precision Electromagnetic Measurements (CPEM 2018) - Paris, France (2018.7.8-2018.7.13)] 2018 Conference on Precision Electromagnetic Measurements (CPEM 2018) - Epitaxial Graphene p-n Junctions
摘要： We report the fabrication and measurement of top gated epitaxial graphene p-n junctions where exfoliated hexgonal boron nitride (hBN) is used as the gate dielectric. The four terminal longitudinal resistance across a single junction is well quantized at RK?90 (= 25812.807 ?) with a relative uncertainty of 10?7. Our work opens the possibility to realize programmable electrical resistance standards using external gating.
关键词： resistance standard,quantum Hall effect,graphene p-n junction,Epitaxial graphene
更新于2025-09-10 09:29:36
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Schottky Junction Vertical Channel GaN Static Induction Transistor with a Sub-Micrometer Fin Width
摘要： GaN-based vertical transistors have demonstrated its excellent properties for high-power and high-frequency electronic devices. This work introduces a GaN-based static induction transistor (SIT) which is another form of vertical GaN transistors without requiring any p-type GaN and gate dielectrics for its operation. Processing strategy to generate the GaN SIT with a sub-micrometer fin width involves photoresist (PR)-assisted planarization with an understanding of dry etch parameters for the planar PR surface. The efficacy of this process is demonstrated by the device’s triode-like output characteristics with high current density (0.65 kA cm?2) and low ON resistance (1.48 mΩ cm2) at 1 V of drain voltage. In addition, the electrical properties such as current density and modulation are examined depending on the fin width of GaN SIT. The result reveals that the size reduction in the GaN SIT utilizing the sub-micrometer fin as a channel could increase the current modulation, but it could decrease the current density because of the raised potential minima due to the depletion region overlap. It is believed that the GaN SIT demonstrating high blocking voltage and low ON resistance would present a very promising class of transistor for next-generation high-power and high-frequency electronics.
关键词： Schottky junction,vertical channel,sub-micrometer dimension,GaN,static induction transistors
更新于2025-09-10 09:29:36
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[IEEE 2018 Conference on Precision Electromagnetic Measurements (CPEM 2018) - Paris, France (2018.7.8-2018.7.13)] 2018 Conference on Precision Electromagnetic Measurements (CPEM 2018) - Three Volt Pulse-Driven Josephson Arbitrary Waveform Synthesizer
摘要： We describe a new generation of Josephson Arbitrary Waveform Synthesizers that generate programmable ac waveforms with an rms amplitude of 3 V and, at 1 kHz, have a quantum locking range greater than 1 mA. This system has two chips with a total of 204 960 Josephson junctions (JJs) co-located on a cryocooler. To test for systematic errors, we phase-shift by 180° the waveform generated by half the JJs (102 480 JJs) to produce an approximate null. The measured residual of 51 nV rms implies a relative agreement of 3 parts in 108 between the two halves of the system.
关键词： Digital-analog conversion,signal synthesis,voltage measurement,superconducting integrated circuits,Josephson junction arrays,measurement standards
更新于2025-09-10 09:29:36
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[IEEE 2018 Conference on Precision Electromagnetic Measurements (CPEM 2018) - Paris, France (2018.7.8-2018.7.13)] 2018 Conference on Precision Electromagnetic Measurements (CPEM 2018) - AC Voltage Measurements up to 120 V with a Josephson Arbitrary Waveform Synthesizer and an Inductive Voltage Divider
摘要： We use a precision inductive voltage divider and a lock-in amplifier to extend the voltage range of a Josephson arbitrary waveform synthesizer with a maximum voltage of 250 mV rms to provide accurate voltage measurements up to 120 V. Experimental results show that the output of the JAWS can be extended to high voltages with uncertainties of a few microvolts per volt or less, depending on the voltage amplitude and frequency.
关键词： quantum voltage standards,measurement array,Inductive voltage divider,standards,Josephson junction techniques
更新于2025-09-10 09:29:36
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[IEEE 2018 Conference on Precision Electromagnetic Measurements (CPEM 2018) - Paris, France (2018.7.8-2018.7.13)] 2018 Conference on Precision Electromagnetic Measurements (CPEM 2018) - Josephson Arbitrary Waveform Synthesizer as a Reference Standard for the Measurement of the Phase of Harmonics in Distorted Signals
摘要： We use the Josephson arbitrary waveform synthesizer to provide traceability for the phase of the harmonics, relative to its fundamental, of a distorted waveform. For distorted waveforms with rms values in the range from 0.154 V to 0.2 V and harmonic magnitudes from 5% to 40 % of the fundamental, our system can generate odd harmonics up to the 39th with phase uncertainties from 0.002° to 0.010° (k=2.0), depending on the harmonic number and harmonic magnitude.
关键词： Josephson junction array,measurement techniques,measurement quantum voltage standards,standards,phase measurement,spectrum analysis
更新于2025-09-10 09:29:36
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[Lecture Notes in Electrical Engineering] Advances in Signal Processing and Communication Volume 526 (Select Proceedings of ICSC 2018) || Fabrication and Characterization of Photojunction Field-Effect Transistor
摘要： In this article, ZnO Quantum Dot (QD)-based photojunction ?eld-effect transistor (photo-JFET) has been fabricated for the detection of ultraviolet (UV) spectrum. The effects of photojunction between the ZnO Quantum Dots (QDs) and deep work function transparent MoO2 is analyzed under the illumination of UV. The illuminated optical power density acts as a ?oating gate for the JFET. The device was fabricated on a glass substrate using interdigitated electrodes (Ag) followed by ZnO QDs layer and MoO2. The dark current between source and drain was found minimum, 2.79 μA/cm2, in the case of photojunction as compared to the metal semiconductor metal (MSM)ZnO QDs photoconductor 19.32 μA/cm2 at an applied bias of 10 V. The reduction in dark current is attributed due to the effect of the junction formed between ZnO QDs and MoO2 with the recti?cation ratio of ~347. The MoO2 depletes the ZnO QDs channel between the electrodes and reduces the dark current which in turn helps to improved photodetector characteristics.
关键词： Schottky junction,Photo-JFET,ZnO quantum dots
更新于2025-09-10 09:29:36
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Excitonic Tunneling in the AB-bilayer Graphene Josephson Junctions
摘要： We have considered the AB-stacked bilayer graphene tunnel junction construction. The bilayers are supposed to be in the charge equilibrium states and at the half-filling in each of the electronic layers of the construction and at each value of the external gate potential. By considering the interacting bilayers in both sides of the junction and by taking into account both intralayer and interlayer Coulomb interaction effects, we have calculated the normal and excitonic tunnel currents through the junction. The electronic band renormalizations have been taken into account, due to the excitonic pairing effects and condensation in the BLGs. The exact four-band energy dispersions, including the excitonic renormalizations, have been used for the bilayers without any low-energy approximation. The normal and excitonic tunneling currents have been calculated for different values of the gate potential and for different values of the interlayer interaction parameters in both sides of the tunnel junction. We demonstrate the existence of the excitonic Josephson current through the junction which persist even for the non-interacting bilayer graphene junction. For the non-interacting case, the mechanism of the excitonic condensates formation and tunneling between the condensates is attributed to the interlayer hopping between the layers. The role of the charge neutrality point has been discussed in details.
关键词： Exciton condensation,Excitonic pairing,Josephson junction,Bilayer graphene
更新于2025-09-10 09:29:36
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Self-constructed facet junctions on hexagonal CdS single crystals with high photoactivity and photostability for water splitting
摘要： Crystal facets engineering of semiconductor catalysts with different exposed facets has been proven as a versatile approach to enhance their photocatalytic performance. Herein, for the first time, a facet-junction engineered hexagonal CdS single crystal with exposing {0001} and {10 0} facets was synthesized by hydrothermal reaction via adjusting the molar ratio of S2-/Cd2+ precursor. The co-exposed {0001} and {10 0} facets on hexagonal CdS single crystals with continuous band bending and well-defined epitaxial interfaces showed highly efficient visible-light-induced H2 evolution. The maximum photocatalytic H2 production rate of 24.33 mmol h?1g?1 is obtained over the facet-junction engineered hexagonal CdS-5 single crystals with an apparent quantum efficiency of 11.18% at 470 nm, which is about 5.27 times greater than CdS-1 nanoparticles. Also, superior photostability is also achieved, even after 25 consecutive cycles during 100 h light irradiation keeping impregnated in strong alkaline sacrificial agent beyond 20 days, the initial photoactivity is still remained. The enhanced photocatalytic H2 evolution activity and photostability can be ascribed to the type-II band alignment between the co-exposed {0001} and {10 0} facets that significantly promoted the separation rate of photo-generated electrons and holes. And the small amount of sulfur vacancies are also benefit for the photocatalytic hydrogen evolution activity of CdS-5. The time-resolved fluorescence (TRPL) decay and photoelectrochemical test further proved the effective spatial charge separation. This work provides a feasible and simple strategy for designing of facet-junction engineered CdS single crystals with highly efficient photocatalytic activity and unprecedented photostability.
关键词： hexagonal CdS single crystals,{0001} facets,photocatalytic hydrogen evolution,facet junction
更新于2025-09-10 09:29:36
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Barrier Height Inhomogeneity in Mixed-dimensional Graphene/Single CdSe Nanobelt Schottky Junctions
摘要： Mixed-dimensional graphene/single CdSe nanobelt (NB) Schottky junctions are fabricated and the influence of Schottky barrier inhomogeneity on the electrical transport mechanism is investigated. The ideality factor increases and the zero-bias Schottky barrier height (SBH) decreases monotonically, as temperature decreases from 300 to 80 K. The temperature-dependent electrical transport characteristics can be explained by the SBH inhomogeneity, which may arise from the inevitable grain boundaries, topographic corrugation and charge puddles in the as-fabricated graphene, surface states and nonuniform dopant concentration in CdSe NB. We use a spatial potential fluctuation model to analyze the conduction mechanism, where the SBH with a Gaussian distribution is assumed. The standard deviations of SBH distribution are up to 13.06% and 14.09% of the mean value of zero-bias SBH in 80–140 K and 140–300 K, respectively, implying strong SBH inhomogeneity in typical graphene/CdSe NB junctions. This work reveals fundamental physical properties in the graphene/CdSe NB interfaces, and might contribute to the future design and implementation of graphene based nano-devices.
关键词： Graphene,inhomogeneity,CdSe Nanobelt,Schottky junction
更新于2025-09-10 09:29:36