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oe1(光电查) - 科学论文

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出版时间
  • 2019
研究主题
  • FSO Communication System
  • Subcarrier Intensity Modulation
  • Atmospheric Turbulence
  • Bit Error Rate
  • Average Irradiance
应用领域
  • Optoelectronic Information Science and Engineering
机构单位
  • Galgotias College of Engineering and Technology
347 条数据
?? 中文（中国） ▾

  • Contactless Optical Characterization of Carrier Dynamics in Free-Standing InAs-InAlAs Core-Shell Nanowires on Silicon

    摘要： Contactless time-resolved pump-probe and external quantum efficiency measurements were performed on epitaxially grown free-standing wurtzite indium arsenide/indium aluminum arsenide (InAs-InAlAs) core-shell nanowires on Si (111) substrate from 77K to 293K. The first independent investigation of Shockley-Read-Hall, radiative and Auger recombination in InAs-based NWs is presented. Although the Shockley-Read Hall recombination coefficient was found to be at least two orders of magnitude larger than the average experimental values of other reported InAs materials, the Auger recombination coefficient was reported to be ten-fold smaller. The very low Auger and high radiative rates result in an estimated peak internal quantum efficiency of the core-shell nanowires as high as 22% at 77K, making these nanowires of potential interest for high efficiency mid-infrared emitters. A greater than two-fold enhancement in minority carrier lifetime was observed from capping nanowires with a thin InAlAs shell due to passivation of surface defects.

    关键词： Auger recombination rate,radiative,Shockley-Read-Hall,Pump-probe spectroscopy,core-shell nanowires,surface/interface recombination velocity,minority carrier lifetime

    更新于2025-09-23 15:23:52

  • Ultrathin GeSe Nanosheets: from Systematic Synthesis, to Studies of Carrier Dynamics and Applications for High Performance UV-Vis Photo-Detector

    摘要： Owing to the attractive energy band properties, black phosphorus (BP)-analogue semiconductor, germanium selenide (GeSe), shows a promising potential applied for optoelectronic devices. Herein, ultrathin GeSe nanosheets were systematically prepared via a facile liquid phase exfoliation (LPE) approach, with controllable nano-scale thickness. Different from BP, ultrathin GeSe nanosheets exhibits a good stability under both liquid and ambient conditions. Besides, its ultrafast carrier dynamics was probed by transient absorption spectroscopy. We showed that the GeSe nanosheets-based photo-detector exhibits excellent photoresponse behaviors ranging from ultraviolet (UV) to the visible regime, with high responsivity and low dark current. Furthermore, the detective ability of such a device can be effectively modulated by varying the applied bias potential, light intensity and concentration of electrolyte. Generally, our present contribution could not only supply fundamental knowledge of GeSe nanosheets-based photoelectrochemical (PEC)-type device, but also offer a guidance to extend other possible semiconductor materials in the application of PEC-type photo-detector.

    关键词： photoelectrochemical,photo-detector,liquid phase exfoliation,carrier dynamics,GeSe nanosheets

    更新于2025-09-23 15:23:52

  • Cation disorder and epitaxial strain modulated Drude–Smith type terahertz conductivity and Hall-carrier switching in Ca <sub/> 1? <i>x</i> </sub> Ce <sub/><i>x</i> </sub> RuO <sub/>3</sub> thin films

    摘要： The CaRuO3 is a non-Fermi liquid pseudo-cubic perovskite with a magnetic ground state on the verge of phase transition and it lies in the vicinity of the quantum critical point. To understand the sensitivity of its ground state, the effects of subtle aliovalent chemical disorder on the static and high frequency dynamic conductivity in the coherently strained structures were explored. The Ce-doped Ca1?xCexRuO3 (0 ? x ? 0.1) thin films were deposited on LaAlO3 (1 0 0) and SrTiO3 (1 0 0) substrates and studies for low-energy terahertz (THz) carrier dynamics, dc transport and Hall effect. These compositions exhibited a very effective and unusual Hall-carrier switching in both compressive and tensile strain induced epitaxial thin films. The dc resistivity depicts a switching from a non-Fermi liquid to a Fermi liquid behavior without any magnetic phase transition. A discernible and gradual crossover from Drude to Drude–Smith THz dynamic optical conductivity was observed while traversing from pure to 10% Ce-doped CaRuO3 films. Overall, a nearly Fermi liquid behavior, effective carrier switching and unusual features in THz conductivity, were all novel features realized for the first time in physically and/or chemically modified CaRuO3. These new phases highlight the novel subtleties and versatility of the systems lying near the quantum critical point.

    关键词： epitaxial strain,terahertz,allovalent doping,Hall carrier switching

    更新于2025-09-23 15:23:52

  • Numerical analysis of single-point spectroscopy curves used in photo-carrier dynamics measurements by Kelvin probe force microscopy under frequency-modulated excitation

    摘要： In recent years, the investigation of the complex interplay between the nanostructure and photo-transport mechanisms has become of crucial importance for the development of many emerging photovoltaic technologies. In this context, Kelvin probe force microscopy under frequency-modulated excitation has emerged as a useful technique for probing photo-carrier dynamics and gaining access to carrier lifetime at the nanoscale in a wide range of photovoltaic materials. However, some aspects about the data interpretation of techniques based on this approach are still the subject of debate, for example, the plausible presence of capacitance artifacts. Special attention shall also be given to the mathematical model used in the data-fitting process as it constitutes a determining aspect in the calculation of time constants. Here, we propose and demonstrate an automatic numerical simulation routine that enables to predict the behavior of spectroscopy curves of the average surface photovoltage as a function of a frequency-modulated excitation source in photovoltaic materials, enabling to compare simulations and experimental results. We describe the general aspects of this simulation routine and we compare it against experimental results previously obtained using single-point Kelvin probe force microscopy under frequency-modulated excitation over a silicon nanocrystal solar cell, as well as against results obtained by intensity-modulated scanning Kelvin probe microscopy over a polymer/fullerene bulk heterojunction device. Moreover, we show how this simulation routine can complement experimental results as additional information about the photo-carrier dynamics of the sample can be gained via the numerical analysis.

    关键词： Kelvin probe force microscopy,nanostructured photovoltaics,numerical simulations,photo-carrier dynamics,carrier dynamics,carrier recombination,carrier lifetime

    更新于2025-09-23 15:22:29

  • Design of InP Based High Speed Photodiode for 2 μm Wavelength Application

    摘要： In this paper, we proposed and designed the high speed uni-traveling carrier photodiodes operating beyond 2 μm. InGaAs/GaAsSb type-II multiple quantum wells (MQWs) were used as the absorption region of uni-traveling carrier photodiode to have optical response beyond 2 μm. A rate equation model was developed to study the bandwidth characteristics of this photodiode. The carrier dynamics of the carrier sweeping out process was discussed, and the structure parameters of the quantum wells were optimized. Result shows a 3-dB bandwidth over 40 GHz can be achieved with the optimized design. We also studied the feasibility of dual depletion PIN (DD-PIN) photodiode with MQWs absorber. The optimized DD-PIN photodiode could achieve similar bandwidth under relatively high-bias condition.

    关键词： high speed photodiodes,type-II quantum well,Carrier dynamic,uni-traveling carrier photodiode

    更新于2025-09-23 15:22:29

  • Microscopic FCA System for Depth-Resolved Carrier Lifetime Measurement in SiC

    摘要： For high voltage SiC bipolar devices, carrier lifetime is an important parameter, and for optimization of device performance, we need to control the distribution of the carrier lifetime in a wafer. So far, there have been limited systems for depth-resolved carrier lifetime measurements without the necessity of making a cross sectional cut. In this study, we adopted a free carrier absorption technique and made local overlapping of the probe laser light with excitation laser light to develop depth-resolved carrier lifetime measurements. We named the developed system a microscopic FCA system and demonstrated measurement results for samples with and without intentional carrier lifetime distribution.

    关键词： free carrier absorption,4H-SiC,carrier lifetime

    更新于2025-09-23 15:22:29

  • [IEEE 2018 International Conference on Advanced Science and Engineering (ICOASE) - Duhok (2018.10.9-2018.10.11)] 2018 International Conference on Advanced Science and Engineering (ICOASE) - An ICI Reduction Based on PAPR Clipping in Coherent Optical OFDM System

    摘要： The Inter-Carrier Interference (ICI) compensation for Coherent Optical Orthogonal Frequency Division Multiplexing (CO-OFDM) system has been studied in this paper. The purpose behind is to investigate the presence of ICI due to the impact of Laser Phase Noise (LPN) and Fiber Non-Linearity (FNL). Thereby, we propose a simple clipping scheme which represents an effective distortion algorithm to decrease the Peak to Average Power Ratio (PAPR) for 4QAM system. The method exhibits a significant process on ICI cancellation in CO-OFDM system. The OFDM signal is basically transmitted along 550km distance rated at 10Gbps single mode fiber for the coherent optical mode. The new findings show that the receiver sensitivity is highly improved below 10-3 FEC for laser power 5dBm; and archives about 1dBm to 2.4dBm when laser power becomes 8dBm at a typical clipping ratio of 0.6. In particular, the system exhibits a good performance over a 385km transmission distance in comparison to the conventional CO-OFDM. As a result, the proposed clipping shows that the system can enhance its the performance by reducing ICI in the CO-OFDM system; in addition to present a high robustness in BER metric against FNL by a clear reduction in PAPR.

    关键词： Coherent Optical Orthogonal Frequency Division Multiplexing (CO-OFDM),Inter-Carrier Interference (ICI),Peak to Average Power Ratio (PAPR),Fiber Nonlinearity (FNL),Bit Error Rate (BER),Laser Phase Noise (LPN)

    更新于2025-09-23 15:22:29

  • The Magnetic Properties of 1111-type Diluted Magnetic Semiconductor (La1?xBax)(Zn1?xMnx)AsO in the Low Doping Regime

    摘要： We investigated the magnetic properties of (La1?xBax)(Zn1?xMnx)AsO with x varying from 0.005 to 0.05 at an external magnetic field of 1000 Oe. For doping levels of x ≤ 0.01, the system remains paramagnetic down to the lowest measurable temperature of 2 K. Only when the doping level increases to x = 0.02 does the ferromagnetic ordering appear. Our analysis indicates that antiferromagnetic exchange interactions dominate for x ≤ 0.01, as shown by the negative Weiss temperature fitted from the magnetization data. The Weiss temperature becomes positive, i.e., ferromagnetic coupling starts to dominate, for x ≥ 0.02. The Mn-Mn spin interaction parameter |2J/kB| is estimated to be in the order of 10 K for both x ≤ 0.01 (antiferromagnetic ordered state) and x ≥ 0.02 (ferromagnetic ordered state). Our results unequivocally demonstrate the competition between ferromagnetic and antiferromagnetic exchange interactions in carrier-mediated ferromagnetic systems.

    关键词： ferromagnetic ordering,ferromagnetic coupling,antiferromagnetic exchange interaction,carrier-mediated

    更新于2025-09-23 15:22:29

  • Real-Time Demonstration of Optimized Spectrum Usage with LSA Carrier Aggregation

    摘要： Mobile broadband networks will face a tremendous growth in data traffic demand over the next 20 years. A key requirement for the evolution of radio access networks is the increase in the amount of spectrum and optimized spectrum usage, in order to meet future service demands. More efficient spectrum use will come with evolving technology features and novel spectrum sharing models. Candidates for technology improvements are higher order and massive MIMO systems, cooperative base stations and CoMP techniques, highly optimized resource allocation algorithms, network densification with inter-cell interference management and highly flexible carrier aggregation techniques to extend spectrum. In this paper, we will highlight carrier aggregation combined with flexible spectrum assignment and use of spectrum databases following novel licensing schemes. We give an overview of LSA activities, present a 3CA demonstration platform enabling the LSA concept and discuss its implementation constraints.

    关键词： carrier aggregation,real-time demonstrator,authorized shared access,licensed shared access,spectrum sharing

    更新于2025-09-23 15:22:29

  • First-principles study of the surface reparation of ultrathin InSe with Se-atom vacancies by thiol chemistry

    摘要： Utilizing first-principles calculations, the surface reparation of monolayer InSe with Se-atom vacancies by thiol chemistry was studied. The geometrical structures and electronic properties of monolayer InSe with Se-atom vacancies were evaluated before and after reparation by S atoms, benchmarked against defect-free case. The parameters of bond lengths, band gaps and carrier mobilities can be recovered to the standard of pristinely defect-free structure. Moreover, the interaction of S atom with complete part of monolayer InSe was also investigated. S atom cannot adsorb on the surface without Se-atom vacancies, while it can substitute Se atom or insert into the interior of monolayer InSe. And the insertion was able to induce a decrease by one order of magnitude. It was demonstrated that thiol chemistry was an effective method to repair Se-atom vacancies and maintain its oxidation resistance, while the insertion of S atom into the interior of monolayer InSe should be avoided.

    关键词： Indium selenides,Carrier mobility,Se-atom vacancies,Band gap,First-principles

    更新于2025-09-23 15:22:29