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Semiconductor Systems (semiconductor + system)
Selected AbstractsAtomic Structure and Electrical Properties of In(Te) Nanocontacts on CdZnTe(110) by Scanning Probe MicroscopyADVANCED FUNCTIONAL MATERIALS, Issue 2 2010Gili Cohen-Taguri Abstract Understanding complex correlations between the macroscopic device performance (largely dependent on the character of the metal,semiconductor contact) and the metallurgy of contact formation on the atomic level in cadmium zinc telluride (CdZnTe) radiation detectors remains a formidable challenge. In this work, an effort towards bridging that macro,nano knowledge gap is made by conducting a series of controlled experiments aimed at correlating electrical properties of the In contact to n-type CdZnTe(110) surface with the step-by-step process of contact formation. This can only be achieved by using high spatial resolution techniques, capable of conducting highly localized measurements on the nano- and sub-nanoscale, such as scanning probe microscopy. Scanning tunneling microscopy is used in situ to monitor the behavior of various In atom coverages on an atomically flat and ordered CdZnTe surface under well-controlled molecular beam epitaxial conditions in ultra-high vacuum. Electrical derivatives of atomic force microscopy are used to measure the electrical contact properties, such as contact potential difference and spreading resistance in torsion resonance tunneling mode. It is concluded that In atoms preferentially reacted with Te atomic-rows already at room temperature, forming nanometric patches of indium,telluride Schottky-type contacts. The methods developed in this study, in terms of both nanocontact fabrication and characterization (especially in terms of electrical properties) should benefit basic and applied research of any metal,semiconductor system. [source] Influence of non-random incorporation of Mn ions on the magnetotransport properties of Ga1,xMnxAs alloysPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 3 2008C. Michel Abstract We study theoretically the influence of a spatially nonrandom incorporation of Mn ions on the magnetotransport in paramagnetic Ga1,xMnxAs alloys. Such a nonrandomness may be introduced during post-growth annealing treatment. We use a resistor-network model for describing the electrical transport of this disordered semiconductor system as a function of temperature and external magnetic field. The model is founded on classical semiconductor band-transport and neglects many-body interactions. The peculiarities of paramagnetic dilute magnetic semiconductors, in particular, the magnetic-field induced changes of the density of states, the broad acceptor-energy distribution, and the interplay of magnetic field independent disorder (due to the alloying of GaAs with Mn) and magnetic field dependent disorder (due to the the Giant Zeeman splitting) are accounted for in a mean-field fashion. We have previously shown that this empirical transport model based on reasonable assumptions and realistic material parameters yields a satisfactory quantitative description of the experimentally obtained temperature and magnetic-field dependence of the resistivity of Ga0.98Mn0.02As samples annealed at different temperatures. For Ga1,xMnxAs alloys annealed at temperatures above 500 °C where structural changes lead to the formation of MnAs clusters, the transport is dominated by the paramagnetic GaAs:Mn host matrix as the cluster density is below the percolation threshold. We will show that in this situation the transport results can only be explained accounting for a nonrandom Mn distribution. Thus the analysis shown here provides further understanding of the annealing-induced changes of the transport properties in dilute magnetic III-Mn-V semiconductors. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Controlled Synthesis of CdSe Nanowires by Solution,Liquid,Solid MethodADVANCED FUNCTIONAL MATERIALS, Issue 22 2009Zhen Li Abstract Semiconductor nanowires prepared by wet chemical methods are a relatively new field of 1D electronic systems, where the dimensions can be controlled by changing the reaction parameters using solution chemistry. Here, the solution,liquid,solid approach where the nanowire growth is governed by low-melting-point catalyst particles, such as Bi nanocrystals, is presented. In particular, the focus is on the preparation and characterization of CdSe nanowires, a material which serves a prototype structure for many kinds of low dimensional semiconductor systems. To investigate the influence of different reaction parameters on the structural and optical properties of the nanowires, a comprehensive synthetic study is presented, and the results are compared with those reported in literature. How the interplay between different reaction parameters affects the diameter, length, crystal structure, and the optical properties of the resultant nanowires are demonstrated. The structural properties are mainly determined by competing reaction pathways, such as the growth of Bi nanocatalysts, the formation and catalytic growth of nanowires, and the formation and uncatalytic growth of quantum dots. Systematic variation of the reaction parameters (e.g., molecular precursors, concentration and concentration ratios, organic ligands, or reaction time, and temperature) enables control of the nanowire diameter from 6 to 33,nm, while their length can be adjusted between several tens of nanometers and tens of micrometers. The obtained CdSe nanowires exhibit an admixture of wurtzite (W) and zinc blende (ZB) structure, which is investigated by X-ray diffraction. The diameter-dependent band gaps of these nanowires can be varied between 650 and 700,nm while their fluorescence intensities are mainly governed by the Cd/Se precursor ratio and the ligands used. [source] Self-assembled quantum dot formation induced by surface energy change of a strained two-dimensional layerPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 3 2004Frank Tinjod Abstract To account for the occurrence (or not) of the Stranski-Krastanow (SK) transition (two-dimensional to 3D change of surface morphology) during the epitaxial growth of various lattice-mismatched semiconductor systems, we present a simple equilibrium model taking into account not only the lattice mismatch, but also the dislocation formation energy and the surface energy. It demonstrates the importance of these parameters especially for II,VI systems such as CdTe/ZnTe and CdSe/ZnSe. For II,VIs indeed, as misfit dislocations are easier to form than in III,Vs (such as InAs/GaAs) or IV systems (Ge/Si), the 3D elastic transition is short-circuited by the plastic one. Nevertheless, by lowering surface energy, telluride and selenide quantum dots can also be grown as predicted by our model and as evidenced experimentally by reflection high-energy electron diffraction (RHEED), atomic force microscopy and optical measurements. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Diamagnetic and nonlinear Zeeman shifts in spatially separated electron and hole layers of semiconductor heterostructures with disorderPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 2 2003J. Desforges Abstract The effect of the diamagnetic shift on the formation of excitons is investigated for double layer semiconductor systems in which electrons and holes are spatially separated. The effect of disorder due to interface roughness of the double layer structures is included in the calculation of exciton density. Numerical calculations are performed based on an effective lattice-gas model where the electron,hole system is divided into unit cells. The exciton density is calculated by using the partition function method. The effect of the nonlinear Zeeman splitting is also included in the numerical calculations. It is found that the density of the optically allowed exciton states (excitons with Sz = 0) increases under the influence of either or both the diamagnetic and the nonlinear Zeeman shifts. [source] Influence of the phonon-exciton interaction on exciton-exciton quantum correlation in semiconductor microcavitiesPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 7 2006S. Portolan Abstract We present an extension of the previous descriptions based on the Dynamics Controlled Truncation Scheme of light-matter interaction beyond mean-field, including the microscopic description of the exciton-photon interaction. This enables the microscopic analysis of the influence of decoherence and noise on the polariton quantum correlations originating from nonlinear optical processes. We expand the operators involved in the dynamics in terms of exact eigenstates of the electron system, the photon and phonon operators and treat phonon-assisted transitions within the Markov approximation. In particular, we present quantum Heisenberg-Langevin equations describing light-induced excitations in semiconductor systems interacting with the phonon bath. This theoretical framework is applied to study the influence of dephasing and noise due to photoluminescence on polariton quantum correlations generated by parametric emission in microcavities. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Proceedings of the 5th International Conference on Nitride Semiconductors (ICNS-5)PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 7 2003Hiroshi Amano The Fifth International Conference on Nitride Semiconductors (ICNS-5) was held at Nara-Ken New Public Hall in Nara, Japan, 25,30 May 2003. This conference series focuses on recent advances in GaN and related materials. It covers scientific and technological developments associated with these materials, their processing and devices. The objective of this conference was to provide a forum for active nitride researchers to exchange their knowledge by presenting their latest results and by carrying out in-depth technical discussions. This conference followed the tradition of the four previous conferences and focused on all aspects of nitride semiconductor systems, which include compounds involving AlInGaN, GaNAsP, AlSiCN and other materials containing nitrogen as one of the major constituents. [source] Proceedings of the International Workshop on Nitride Semiconductors (IWN 2002)PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 1 2003Axel Hoffmann These proceedings contain papers presented at the International Workshop on Nitride Semiconductors (IWN 2002) which was held in Aachen, Germany, 22,25 July 2002. The objective of this workshop was to provide a forum for active nitride researchers to gather and promote scientific and technical discussions. It covered all aspects of nitride semiconductor systems such as AlInGaN, AlGaNAsP, and other materials containing nitrogen as one of the major constituents. [source] | ||||||||||