- 标题
- 摘要
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- 实验方案
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[IEEE 2018 International Semiconductor Conference (CAS) - Sinaia, Romania (2018.10.10-2018.10.12)] 2018 International Semiconductor Conference (CAS) - Second Harmonic Generation: A Non-Destructive Characterization Method for Dielectric-Semiconductor Interfaces
摘要： This paper reviews the application of second harmonic generation (SHG) to characterize dielectric-semiconductor interfaces in microelectronics and photovoltaics. Based on non-linear optics, the method is non-destructive, so particularly advantageous for thin films. The theoretical background shows the possibility to access the electric field at interfaces and consequently to have a non-destructive measurement for interface state densities or fixed charges in oxides. Two more detailed examples of application of SHG characterization will be shown: passivation of silicon using thin film deposited alumina and interface analysis of silicon-on-insulator substrates.
关键词： interface states,dielectric-semiconductor interfaces,fixed oxide charges,interface electric field,second harmonic generation
更新于2025-09-04 15:30:14
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Comparison of Optical Single Sideband Techniques for THz-over-fiber Systems
摘要： The use of single sideband (SSB) signals and envelope detection is a promising approach to enable the use of economic free-running lasers in photonic THz communications. To combat the signal-signal beat interference (SSBI) associated with envelope detection, broad guard bands (GBs) may be used given the large unregulated spectrum available at THz frequencies (100 GHz – 10 THz). In this scenario, the conventional way of generating SSB signals through a digital SSB filter (here referred to as the CSSB scheme) would require quite high analog digital-to-analog converter (DAC) bandwidths. Digital virtual SSB (DVSSB) and analog virtual SSB (AVSSB) have been proposed in direct-detection optical systems for relaxing the DAC bandwidth requirements. In this paper, we compare the three techniques through simulations and implement them, for the first time, in a THz-over-fiber (ToF) system operating at 250 GHz. For the transmission experiments we employ 5 GBd 16-QAM signals with three different GBs (5.5 GHz, 4.75 GHz and 3.5 GHz). The simulations show that the best performance is obtained with the AVSSB technique, while the worst is obtained with the DVSSB scheme, where the quality of the generated sideband degrades with carrier-to-sideband power ratio. In the experimental transmissions, where receiver noise was the main source of noise, similar behavior was found between the three techniques. At the 3.5 GHz GB, however, the DVSSB exhibited a penalty of 1 dB with respect to the other two. This is likely to be due to nonlinear distortions caused by the increase in the virtual tone power.
关键词： microwave photonics,Broadband communication,semiconductor lasers,photonic integrated circuits,digital signal processing,envelope detectors,optical mixing,millimeter wave communication
更新于2025-09-04 15:30:14
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[Institution of Engineering and Technology 12th European Conference on Antennas and Propagation (EuCAP 2018) - London, UK (9-13 April 2018)] 12th European Conference on Antennas and Propagation (EuCAP 2018) - Engineering Modes of PT Symmetric Photonic Crystals
摘要： This work explores the effects of parity-time (PT) symmetry on the modes of photonic crystal defect waveguides. Two designs are considered. In the ?rst, the defect modes are protected from PT transitions, but edge modes in the complex conjugate frequency regime appear. In the second design, the defect modes exhibit thresholdless PT transitions.
关键词： photonic crystals,optical waveguides,parity-time symmetry,photonic integrated circuits,semiconductor waveguides
更新于2025-09-04 15:30:14
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[Institution of Engineering and Technology 12th European Conference on Antennas and Propagation (EuCAP 2018) - London, UK (9-13 April 2018)] 12th European Conference on Antennas and Propagation (EuCAP 2018) - Time-modulated Periodic Systems with PT Symmetry
摘要： This work explores the effects of parity-time (PT) symmetry in time-modulated periodic systems. Mechanisms for dynamic tunability of exceptional points are presented. We show that synthetic linear momentum imparted by time-modulation leads to uni-directional exceptional points. Such structures could see application in uni-directional lasers with tunable directionality.
关键词： semiconductor lasers,photonic crystals,distributed feedback lasers,time-varying circuits,parity-time symmetry,time-varying systems,optical modulation
更新于2025-09-04 15:30:14
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Study of anharmonicity in pure and doped InSe by Raman scattering
摘要： With the help of temperature dependence, Raman scattering anharmonic effect of various modes of layered semiconductor InSe over temperature range of 20–650 K has been studied. It was found that with an increase in temperature, anharmonicity will increase. Two and three phonons coupling with optical phonon, are used to describe temperature-induced anharmonicity in the linewidth of Raman modes. It was found that the temperature variation of the phonon parameter can be accounted for well by the cubic term in anharmonic model. To describe line-center shift of Raman modes, a model not considering independently cubic and quartic anharmonicity was used. A similar study has been done for InSe doped with different concentration of GaS dopant. The result of temperature study of InSe doped with GaS revealed that in this case anharmonicity increases with an increase in dopant and an increase in temperature.
关键词： GaS,doping,Raman scattering,Semiconductor,InSe
更新于2025-09-04 15:30:14
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Band-fluctuations model for the fundamental absorption of crystalline and amorphous semiconductors: a dimensionless joint density of states analysis
摘要： We develop a band-fluctuations model which describes the absorption coefficient in the fundamental absorption region for direct and indirect electronic transitions in disordered semiconductor materials. The model accurately describes both the Urbach tail and absorption edge regions observed in such materials near the mobility edge in a single equation with only three fitting parameters. An asymptotic analysis leads to the universally observed exponential tail below the bandgap energy and to the absorption edge model at zero Kelvin above it, for either direct or indirect electronic transitions. The latter feature allows the discrimination between the absorption edge and absorption tails, thus yielding more accurate bandgap values when fitting optical absorption data. We examine the general character of the model using a dimensionless Joint Density of States formalism with a quantitative analysis of a large amount of optical absorption data. Both heavily doped p-type GaAs and nano-crystalline Ga1?xMnxN, as examples for direct bandgap materials, as well as amorphous Si:Hx, SiC:Hx and SiNx, are modeled successfully with this approach. We contrast our model with previously reported empirical models, showing in our case a suitable absorption coefficient shape capable of describing various distinct materials while also maintaining the universality of the exponential absorption tail and absorption edge.
关键词： band-fluctuations model,fundamental absorption,disordered semiconductor materials,absorption edge,Joint Density of States,Urbach tail
更新于2025-09-04 15:30:14
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Piezotronics and piezo-phototronics with third-generation semiconductors
摘要： When uniform strain is applied to noncentrosymmetric semiconductor crystals, which are piezoelectric, static polarization charges are induced at the surface. If the applied strain is not uniform, these charges can even be created inside the crystal. The applied strain affects electronic transport and also photonic processes, and thus can be used to tune the material properties statically or dynamically. As a result, two new fields have emerged, namely piezotronics and piezo-phototronics. This article reviews the history of the two fields and gives a perspective on their applications. The articles in this issue of MRS Bulletin highlight progress in these two fields, and this article places this progress into perspective.
关键词： piezo-phototronics,piezoelectricity,piezotronics,semiconductor transport,third-generation semiconductors
更新于2025-09-04 15:30:14
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Theory of piezotronics and piezo-phototronics
摘要： Piezotronic and piezo-phototronic devices exhibit high performance and have potential applications especially in next-generation self-powered, flexible electronics and wearable systems. In these devices, a strain-induced piezoelectric field at a junction, contact, or interface can significantly modulate the carrier generation, recombination, and transport properties. This mechanism has been studied based on the theory of piezotronics and piezo-phototronics. Simulation-driven materials design and device improvements have been greatly propelled by the finite element method, density functional theory, and molecular dynamics for achieving high-performance devices. Dynamical piezoelectric fields can also control new quantum states in quantum materials, such as in topological insulators, which pave a new path for enhancing performance and for investigating the fundamental physics of quantum piezotronics and piezo-phototronics.
关键词： piezo-phototronics,piezotronics,piezoelectric field,quantum materials,semiconductor physics
更新于2025-09-04 15:30:14
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[IEEE 2018 XV International Scientific Conference on Optoelectronic and Electronic Sensors (COE) - Warsaw, Poland (2018.6.17-2018.6.20)] 2018 XV International Scientific Conference on Optoelectronic and Electronic Sensors (COE) - Wavelet Transform Analysis of Temperature Modulated Gas Sensor Response
摘要： The aim of the study was to evaluate whether it is possible to extract the information about the gas concentration despite the influence of humidity. Commercial semiconductor sensor response was examined under the application of a periodic temperature change. The data was collected using measurement protocol for different concentrations of ammonia at specified levels of relative humidity. In this work we focused on the evaluation of the Discrete Wavelet Transform analysis results obtained during experimental investigation of the single semiconductor gas sensor in the presence of humidified atmosphere containing ammonia. The results of the analysis show that proposed method enable the possibility of determine the low concentrations of ammonia.
关键词： feature extraction,semiconductor gas sensor,discrete wavelet transform,data analysis,temperature modulation
更新于2025-09-04 15:30:14
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PHOTONIC ANALYSIS OF SEMICONDUCTOR FIBONACCI SUPERLATTICES: PROPERTIES AND APPLICATIONS
摘要： In this paper, we theoretically study the phase treatment of re?ected waves in one-dimensional Fibonacci photonic quasicrystals composed of nano-scale fullerene and semiconductor layers. The dependence of the phase shift of re?ected waves for TE mode and TM mode on the wavelength and incident angle is calculated by using the theoretical model based on the transfer matrix method in the infrared wavelength region. In the band gaps of supposed structures, it is found that the phase shift of re?ected wave changes more slowly than within the transmission band gaps. Furthermore, the phase shift decreases with the incident angle increasing for TE mode, and increases with the incident angle increasing for TM mode. Also, for the supposed structures it is found that there is a band gap which is insensitive to the order of the Fibonacci sequence. These structures open a promising way to fabricate subwavelength tunable phase compensators, very compact wave plates and phase-sensitive interferometry for TE and TM waves.
关键词： Fibonacci photonic quasicrystals,TE mode,semiconductor layers,infrared wavelength region,fullerene,phase shift,transfer matrix method,TM mode
更新于2025-09-04 15:30:14