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71.
E. Schll 《Solid-state electronics》1989,32(12):1129-1135
The status of our theoretical understanding of self-generated nonlinear and chaotic oscillations in semiconductors associated with impact ionization of impurity centers is reviewed from the viewpoint of hot electron transport theory. A set of hydrodynamic balance equations for the carrier density, mean momentum and energy is developed. It constitutes, together with Maxwell's equations, a macroscopic nonlinear dynamic system. We discuss various simplified versions of this model, which give rise to local or global bifurcations and hysteresis of limit cycle oscillations, a period-doubling route to chaos, mode-locking and quasiperiodicity, traveling waves, and breathing current filaments. 相似文献
72.
L. Rota
P. Lugli
《Solid-state electronics》1989,32(12):1423-1427The theoretical treatment of electron-electron (e-e) scattering in semiconductor transport has always posed formidable problems, due to the long range and to the non-linearity of the interaction. Here we present a Monte Carlo study of the e-e interaction based on a molecular-dynamics approach. The full long range of the Coulomb interaction is accounted for, and no assumptions are needed on the screening process. This is particularly important when different valleys are involved, and a multi-component plasma has to be simulated. The Monte Carlo algorithm is applied to the study of the relaxation of photo-excited electrons in GaAs looking in particular at the energy exchange between electrons in different valleys. Such type of interaction has never been considered up to now in Monte Carlo simulations. The dependence of the e-e interaction on the electron density is discussed in detail. A comparison with a different approach, that treats the e-e scattering in k-space using a screened potential formulation, is also presented. 相似文献
73.
Uniform carrier injection into the channel of n-MOSFETs generates two types of interface states, depending on the oxide electric field: One is linearly proportional to the injected electron density (Type I), while the other shows a half-power dependence (Type II). Charge-pumping measurements in the temperature range of 77K and 263K show that the type I interface states are located in the mid-gap, while the type II interface states are uniformly distributed in wide energy range. Holes generated at the gate/SiO2 interface or in the oxide are found to be responsible for the type I interface states, while hydrogen or hydrogen compounds diffusing from the interface cause the type II interface states. 相似文献
74.
Hamidreza Esmaielpour Vincent R. Whiteside Jinfeng Tang Sangeetha Vijeyaragunathan Tetsuya D. Mishima Shayne Cairns Michael B. Santos Bin Wang Ian R. Sellers 《Progress in Photovoltaics: Research and Applications》2016,24(5):591-599
InAs/AlAsxSb1 − x quantum wells are investigated for their potential as hot carrier solar cells. Continuous wave power and temperature‐dependent photoluminescence indicate a transition in the dominant hot carrier relaxation process from conventional phonon‐mediated carrier relaxation below 90 K to a regime where inhibited radiative recombination dominates the hot carrier relaxation at elevated temperatures. At temperatures below 90 K, photoluminescence measurements are consistent with type‐I quantum wells that exhibit hole localization associated with alloy/interface fluctuations. At elevated temperatures, hole delocalization reveals the true type‐II band alignment, where it is observed that inhibited radiative recombination due to the spatial separation of the charge carriers dominates hot carrier relaxation. This decoupling of phonon‐mediated relaxation results in robust hot carriers at higher temperatures, even at lower excitation powers. These results indicate type‐II quantum wells offer potential as practical hot carrier systems. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
75.
In this paper we describe an environmentally friendly and sensitive method for the determination of ten primary amines in sewage sludge. The method is based on pressurised hot water extraction (PHWE) followed by simultaneous derivatization with pentafluorobenzaldehyde (PFBAY) and headspace solid-phase microextraction (HS-SPME) and subsequent gas-chromatography ion-trap tandem mass spectrometry (GC-IT-MS-MS) analysis. The influence of the main factors on the PHWE of sludge was optimized by a central composite design. For all species the optimal conditions were water at pH 4 as the extracting solvent, an extraction temperature of 100 °C and an extraction time of 15 min. The separation and detection of the ten amines by GC-IT-MS-MS took just 10 min and the entire process took approximately 1 h. Repeatability and reproducibility between days, expressed as RSD (%) (n = 5), were less than 19 and 24%, respectively. The average limit of detection (LOD) was of 65 μg kg−1 s (range found 9-135) and the average limit of quantification (LOQ) was of 230 μg kg−1 (range found 50-450) of dry weight (d.w.). Under optimized conditions we used this method to determine the compounds in industrial and municipal sewage sludge samples and in sludge from a potable water treatment plant. Methylamine and isobutylamine showed the highest levels in one of the industrial sewage sludge samples (404 and 543 mg kg−1 (d.w.), respectively). To our knowledge, this paper presents for the first time the determination of ten primary amines in sewage sludge samples using PHWE. 相似文献
76.
Chin Chye Teo Swee Ngin Tan Jean Wan Hong Yong Choy Sin Hew Eng Shi Ong 《Journal of chromatography. A》2010,1217(16):2484-2494
Pressurized hot water extraction (PHWE) has become a popular green extraction method for different classes of compounds present in numerous kinds of matrices such as environmental, food and botanical samples. PHWE is also used in sample preparation to extract organic contaminants from foodstuff for food safety analysis and soils/sediments for environmental monitoring purposes. The main parameters which influence its extraction efficiency are namely the temperature, extraction time, flow rates and addition of modifiers/additives. Among these different parameters studied, temperature is described as the most important one. It is reported that the extraction of certain compounds is rather dependent on pressurized water with different applied temperature. Thus, the stability and reduced solubilities of certain compounds at elevated temperatures are highlighted in this review. With some modifications, a scaled-up PHWE could extract a higher amount of desirable compounds from solid and powdered samples such as plant and food materials. The PHWE extracts from plants are rich in chemical compounds or metabolites which can be a potential lead for drug discovery or development of disease-resistant food crops. 相似文献
77.
78.
连续波化学激光器运转时,位于主喷管叶片内的副气流的分流管道壁面将被主喷管叶片加热而形成热壁面。通过3维的数值模拟,分析了单端、双端不同供气方式下,热壁面对分流管道流场特性的影响。热壁面将使总管气流总温沿着气流的流动方向逐渐升高,由此引起的支管入口总温的升高会降低支管的流量。无论是单端供气,还是双端供气,热壁面引起的管道流量波动幅度都要远大于绝热壁面的情况,最大波动幅度达2.16%。对进入总管的气流预热,适当增加供气总温,或将冷却管道与供气管道分开设计,气流总温变化引起的流量波动将会得到一定地抑制。 相似文献
79.
80.