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Search Results: 1 - 10 of 8178 matches for " quantum well injection transit "
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Comparison and Analysis of Two Microwave Equivalent-Circuit Models for Resonant Tunneling Diode

Zhong Ming,Zhang Shilin,Guo Weilian,LIANG Huilai,Mao Luhong,

半导体学报 , 2004,
Abstract: The distinction between two microwave equivalent-circuit models,quasi Esaki tunneling model (QETM) and quantum well injection transit model (QWITM),for the resonant tunneling diode (RTD) is discussed in details,and two groups of circuit parameters are extracted from experiment data by the least square fit method.Both theory analysis and the comparison of fit results demonstrate that QWITM is much more precise than QETM.In addition,the rationality of QWITM circuit's parameters confirms it too.On this basis,the resistive frequency is calculated,whose influence factors and improvement method are simply discussed as well.
Monolithic integration of electroabsorption modulators and tunnel injection distributed feedback lasers using quantum well intermixing

Wang Yang,Pan Jiao-Qing,Zhao Ling-Juan,Zhu Hong-Liang,Wang Wei,

中国物理 B , 2010,
Photo-Detectors Integrated with Resonant Tunneling Diodes
Bruno Romeira,Luis M. Pessoa,Henrique M. Salgado,Charles N. Ironside,José M. L. Figueiredo
Sensors , 2013, DOI: 10.3390/s130709464
Abstract: We report on photo-detectors consisting of an optical waveguide that incorporates a resonant tunneling diode (RTD). Operating at wavelengths around 1.55 μm in the optical communications C band we achieve maximum sensitivities of around 0.29 A/W which is dependent on the bias voltage. This is due to the nature of RTD nonlinear current-voltage characteristic that has a negative differential resistance (NDR) region. The resonant tunneling diode photo-detector (RTD-PD) can be operated in either non-oscillating or oscillating regimes depending on the bias voltage quiescent point. The oscillating regime is apparent when the RTD-PD is biased in the NDR region giving rise to electrical gain and microwave self-sustained oscillations Taking advantage of the RTD’s NDR distinctive characteristics, we demonstrate efficient detection of gigahertz (GHz) modulated optical carriers and optical control of a RTD GHz oscillator. RTD-PD based devices can have applications in generation and optical control of GHz low-phase noise oscillators, clock recovery systems, and fiber optic enabled radio frequency communication systems.
A Probabilistic Method of Characterizing Transit Times for Quantum Particles in Non-Stationary States  [PDF]
Hae-Won Kim, Karl Sohlberg
Journal of Modern Physics (JMP) , 2013, DOI: 10.4236/jmp.2013.48145

We present a probabilistic approach to characterizing the transit time for a quantum particle to flow between two spatially localized states. The time dependence is investigated by initializing the particle in one spatially localized “orbital” and following the time development of the corresponding non-stationary wavefunction of the time-independent Hamiltonian as the particle travels to a second orbital. We show how to calculate the probability that the particle, initially localized in one orbital, has reached a second orbital after a given elapsed time. To do so, discrete evaluations of the time-dependence of orbital occupancy, taken using a fixed time increment, are subjected to conditional probability analysis with the additional restriction of minimum flow rate. This approach yields transit-time probabilities that converge as the time increment used is decreased. The method is demonstrated on cases of two-state oscillations and shown to produce physically realistic results.

Multiple-State Quantum Carnot Engine  [PDF]
Eny Latifah, Agus Purwanto
Journal of Modern Physics (JMP) , 2011, DOI: 10.4236/jmp.2011.211169
Abstract: A multiple-state quantum Carnot engine based on single particle in one dimensional potential well is evaluated. The general forms of adiabatic and isothermal force as well as work are given. We apply them first to the simplest case of two-state system, and then to three-state and general n-state system. The first isothermal expansion starts from single ground state and cease to single highest state. In Addition to the simplest case, isothermal expansions may terminate not to highest state but an intermediate state but with the same of the total expansion. The result is that the efficiency of the multi-state machine could be enhanced by reducing the volume of isothermal expansion for the same of the total volume expansion.
Magnetic-Field Effects on Donor Impurity States in a Quantum Well  [PDF]
Arnold Abramov
World Journal of Condensed Matter Physics (WJCMP) , 2012, DOI: 10.4236/wjcmp.2012.24031
Abstract: Green’s function technique is used to obtain the solution of Shredinger equation for impurity states in a quantum well (QW) under the magnetic field. Binding energy of impurity states is defined as poles of the wave function. We studied effects of the magnetic field magnitude and impurity position on the binding energy. The calculations were performed for both ground and excited states. The dependences of binding energies versus impurity position and magnetic field are presented for GaAs/Al0.3Ga0.7As QW.
Thz Radiation under Tunneling in Asymmetric Double Quatum Wells  [PDF]
Menberu Mengesha, Svetlana Koshvaya, Vadim Mal’nev
Journal of Electromagnetic Analysis and Applications (JEMAA) , 2011, DOI: 10.4236/jemaa.2011.37044
Abstract: The asymmetric parabolic double quantum wells (DQWs) with resonant levels (the ground state energy in one well co-incides with the first excited state energy in another well) is analyzed. The splitting of these levels and the tunneling times are calculated. If the typical life time of the excited state is much smaller than the tunneling time between wells, the charged particle can radiate as a result of the quantum transition from the excited state to the ground state. In the opposite case, the asymmetric DQWs can be treated as a metastable excited nanosystem regardless of that the dipole transition from the excited state to ground state is permitted. The lifetime of this metastable state can be considerably reduced by putting it into a resonant cavity. The possibility of coherent radiation of an ensemble of asymmetric DQWS is discussed.
Analyses of Physical Data to Evaluate the Potential to Identify Class I Injection Well Fluid Migration Risk  [PDF]
Frederick Bloetscher
Journal of Environmental Protection (JEP) , 2014, DOI: 10.4236/jep.2014.56057

Injection wells have been used for disposal of fluids for nearly 100 years. Design of injection well systems has advanced over the years, but environmental concerns due to the potential for migration of injected fluids remain. Fluids range from hazardous materials, to mining waste to treated wastewater. This paper presents an evaluation of wells injecting treated wastewater to assess which create the greatest risk to migration potential. Prior studies have looked at the risks of Class I injection wells for wastewater disposal, but limited data were available at that time. This research involved collecting data and evaluating the differences as a means to predict the potential for fluid migration in the wells. There were four issues that might portend migration: well depth-shallower wells tended to have more migration; the tightness of the confining unit immediately above the injection zone; well age; and the use of tubing and packers. Florida is moving away from tubing and packer wells which may be an indicative of this issue. The results provide a pathway to investigate injection wells in other states.

Optical properties of InGaAsP quantum well for infrared emission investigated by modulation spectroscopy
Optica Applicata , 2005,
Abstract: Modulation spectroscopy, i.e., photoreflectance (PR) and contactless electroreflectance (CER) are very powerful techniques to investigate optical properties of nanostructures. These techniques together with photoluminescence spectroscopy were used for investigation of optical properties of InGaAsP quantum well with infrared emission at 1.55 mm. Samples used in this study were grown by gas source molecular beam epitaxy (MBE) on n-doped (100) InP substrate. Based on the numerical calculations the origin of observed optical transitions has been explained and the energy structure of the investigated samples has been proposed.
Graphene-Semiconductor Quantum Well with Asymmetric Energy Gaps  [PDF]
J. T. Wang, D. S. Guo, G. L Zhao, J. C. Chen, Z. W. Sun, A. Ignatiev
World Journal of Condensed Matter Physics (WJCMP) , 2013, DOI: 10.4236/wjcmp.2013.31012

Semiconductor solar cell (PV cell) has been widely used for generating solar electricity. However, the high cost and severe pollution limits its application. Recently the discovery of graphene may open a door to fabricate a novel solar cell with lower cost and more environmentally friendly. Our proposed solar cell device consists of a graphene strip and two semiconductor strips with different energy gaps attached to the two edges of the graphene strip on a flat plane. This structure is a two-dimensional quantum well. The energy bands of graphene can be described by a two-dimensional Dirac equation centered on hexagonal corners (Dirac points) of the honeycomb lattice Brillouin zone. The 2 D Dirac equation has been solved numerically in this paper. The results indicate that the graphene quantum well possesses very dense quantum energy states which imply that quantum well of this type can absorb sun light with more different frequencies. If we use graphene quantum well to fabricate the photo voltaic cell, the efficiency of converting solar energy to electricity will be enhanced.


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