Papers by Keyword: Quantum Well

Abstract: In this work, some properties of the InAs/InGaAs quantum well (QW) were calculated, such as the wave functions and the charge density of the 2D free electron gas (2DEG) by solving the Poisson- Schroedinger equation. The thinner capping layer gives charge densities forming inside the QW that are higher than the thicker values. The optimal thickness of the capping layer can be 10 nm due to the most stable charge density and fully symmetrical wave functions. Our result indicates that higher charge densities can be found with higher Si-delta doping concentrations. However, the distance of the Si-delta doping also affects the charge population. The charge density linearly decreases with a higher Si-delta doping spacer; the thickness was chosen as 7nm. We performed the growth with different concentrations of Si with optimal thicknesses and compared them with the calculated values. There is good agreement between the simulations and experiments with the lower Si-doping concentrations.

Abstract: In this paper, a color-tunable light emitting diode LED with two laterally arranged single quantum wells (SQWs) is designed, and simulated. In this work, III-nitride materials are used. The structure has been numerically investigated using the ATLAS simulation software. The proposed structure has three electrodes. This gives the opportunity to emit violet (420 nm) or green (560 nm) light individually. Furthermore, it can emit simultaneously a mixture of both colors, and at a certain mixture ratio the white light is obtained with chromaticity coordinates ( x = 0.3113, y = 0.3973). The lateral arrangement of the two SQWs reduces the negative effect of photon absorption; which will give good external quantum efficiency (EQE). The structure has a big importance in the application of the solid-state lighting, especially in the white light generation.

Abstract: This present work is about simulating and analysing a Vertical Cavity Surface Emitting Laser (VCSEL) structure used in optical fibre communication systems. In this paper a VCSEL structure made of seven Quantum Wells of Indium Gallium Arsenide Phosphide (InGaAsP) emitting at 1550 nm is simulated. The device is analysed looking at the following characteristics: Direct current current and voltage (IV) characteristics, light power against electrical bias, optical gain against electrical bias, light distribution over the structure, output power and threshold current. Specification of material characteristics, ordinary physical models settings, initial VCSEL biasing, mesh declarations, declaration of laser physical models, their optical and electrical parameters were defined using Atlas syntax. Mirror ratings and quantum wells are the two main parameters that were studied and analysed to come up with structure trends. By determining important device parameters such as proper selection of the emission wavelength and choice of material; a VCSEL with an output power of 9.5 mW was simulated and compared with other structures.

Abstract: The influence of electromagnetic wave (EMW) on the acous- tomagnetoelectric (AME)effect is studied theoretically in a quantum well. The expression of the AME field is obtained. Thedependences of the AME field on the temperature of system, the frequency of acoustic wave, thefrequency and intensity of electromagnetic wave and the parameters of a Quantum well are nonlinear.These dependences in the case of QW are different and more complex than in the case of bulksemiconductor. The results are numerically calculated and discussed for an GaAs/AGaAs QW. Thegraph of the dependence of the AME field on the frequency of acoustic wave shows that the changesof external magnetic field drag on the change of value of AME field and the change of the positionof AME field. The value of the AME field in case with the intensity of EMW is much bigger than incase without the intensity of EMW.

Abstract: The Shubnikov – de Haas magnetoresistance oscillations in the Quantum well (QW) under the influence of confined acoustic phonons, The theoretical results show that the conductivity tensor, the complex magnetic impedance of the magnetic field, the frequency, the amplitude of the laser radiation, the QW width, the temperature of the system and especially the quantum index m characterizes the confinement of the phonon. The amplitude of the oscillations of the Shubnikov-de Haas impedance decreases with the increase of the influence of the confined acoustic phonons. The results for bulk phonons in a QW could be achieved, when m goes to zero. We has been compared with other studies when perform the numerical calculations are also achieved for the GaAs/AlGaAs in the QW. Results show that The Shubnikov-de Haas magnetoresistance oscillations amplitude decrease when phonon confinement effect increasing and when width L of the QW increases to a certain value, The Shubnikov – de Haas magnetoresistance oscillations amplitude completely disappears can not be observed.

Abstract: We have performed capacitance-voltage (C-V) and deep level transient spectroscopy (DLTS) measurements on Schottky contacts fabricated on triangular defects in 4H-SiC epitaxial layers. These measurements are a case study on the effect of a specific extended defect on the DLTS spectrum in order to contribute to the physical understanding of curious features occasionally observed in DLTS spectra. Our measurements reveal an inversion of the DLTS signal depending on applied voltages and filling pulse lengths, and a step in the C-V characteristic of the Schottky diode. We present a model that qualitatively describes the experimentally obtained data. In this model, we assume that stacking faults within a triangular defect form quantum wells, which can capture electrons from other defects during the DLTS measurement leading to the inversion of the DLTS spectrum. Moreover, by calculating the differential capacitance using a self-consistent Schrödinger-Poisson-Solver, the step in the C-V measurements is reproduced by our model.

Abstract: This paper is devoted to the consideration of currently available studies on obtaining stimulated infrared emission in structures based on HgCdTe quantum wells. Also analysis and interpretation of discussed experimental results are presented in this article.

Abstract: Transport and magnetic properties of δ-Mn doped GaAs/InGaAs/GaAs quantum wells (QW) with various In content were studied at temperatures 4.2K≤T≤300K. Fluctuation potential (FP) appeared to be crucial for transport characteristics of structures under investigation. The magnetic percolation transition was observed at temperature T_p in the range 20 - 40K. The T_p dependence on the In content is nonmonotonic due to the peculiarities of free-carrier mediated exchange interaction mechanisms. The change of the anomalous Hall effect (AHE) sign with decreasing temperature was detected at temperatures close to the T_p. The main reason of the AHE sign change is the variation of contributions of different AHE mechanisms (intrinsic and side-jump) caused by the reduction of spin-dependent scattering intensity with temperature decrease. We believe that our results are the experimental observation of the AHE intrinsic mechanism in 2D.

Abstract: The composing semiconductors became the support privileged of information and the communication, in particular grace to the faster development of Internet, for the systems of telecommunications to high debit, some components are necessary. It is for this reason that of the alternative structures have been proposed: the IV-IV heterostructures or III-V. The most effective components in this domain are the field effect transistors (High Electron Mobility Transistor: HEMT) on IIIV substratum. The present work is dedicated to the contribution to the development of a numeric physical model which based on the influence of the different parameters (physical and geometric) on the parameters characterizing the potential at the interface of a heterostructure in GaAsAl/GaAs. The present work also has aim to characterize dynamics carriers in a HEMT heterostructure which we will consider later a dynamic study of quantum well solar cells in a rigorous and complete manner.

Abstract: The simulation of multicomponent nanoheterostructures (MNH) InGaN for light-emitting diodes (LEDs) was made. The results are presented in graphs, for example, the current-voltage characteristics, the dependence of the internal quantum efficiency (IQE) on the number of quantum wells (QW) and spectral characteristics. The optimal structure of the MNH and the influence of the inhomogeneous distribution of In atoms in the quantum-well region is investigated.