Einstein Relation in Compound Semiconductors and Their Nanostructures

Springer Series in materials science 116 Springer Series in materials science Editors: R. Hull R. M. Osgood, Jr. J. Parisi H. Warlimont The Springer Series in Materials Science covers the complete spectrum of materials physics, including fundamental principles, physical properties, materials theory and design. Recognizing the increasing importance of materials science in future device technologies, the book titles in this series reflect the state-of-the-art in understanding and controlling the structure and properties of all important classes of materials. 99 Self-Organized Morphology 109 Reactive Sputter Deposition in Nanostructured Materials Editors: D. Depla and S. Mahieu Editors: K. Al-Shamery and J. Parisi 110 The Physics of Organic Superconductors 100 Self Healing Materials and Conductors An Alternative Approach Editor:A.Lebed to 20 Centuries of Materials Science Editor: S. van der Zwaag 111 Molecular Catalysts for Energy Conversion 101 New Organic Nanostructures Editors: T. Okada and M. Kaneko for Next Generation Devices Editors: K. Al-Shamery, H.-G. Rubahn, 112 Atomistic and Continuum Modeling andH.Sitter of Nanocrystalline Materials Deformation Mechanisms 102 Photonic Crystal Fibers and Scale Transition Properties and Applications By M. Cherkaoui and L. Capolungo By F. Poli, A. Cucinotta, and S. Selleri 113 Crystallography and the World of Symmetry 103 Polarons in Advanced Materials By S.K. Chatterjee Editor: A.S. Alexandrov 114 Piezoelectricity 104 Transparent Conductive Zinc Oxide Evolution and Future of a Technology Basics and Applications Editors: W. Heywang, K. Lubitz, in Thin Film Solar Cells andW.Wersing Editors: K. Ellmer, A. Klein, and B. Rech 115 Lithium Niobate 105 Dilute III-V Nitride Semiconductors Defects, Photorefraction and Material Systems and Ferroelectric Switching Physics and Technology ByT.VolkandM.Wohlecke¨ Editor:A.Erol 116 Einstein Relation 106 Into The Nano Era in Compound Semiconductors Moore’s Law Beyond Planar Silicon CMOS and Their Nanostructures Editor: H.R. Huff By K.P.Ghatak, S. Bhattacharya, and D. De 107 Organic Semiconductors 117 From Bulk to Nano in Sensor Applications The Many Sides of Magnetism Editors: D.A. Bernards, R.M. Ownes, By C.G. Stefanita and G.G. Malliaras 108 EvolutionofThin-FilmMorphology Modeling and Simulations By M. Pelliccione and T.-M. Lu Volumes 50–98 are listed at the end of the book. Kamakhya Prasad Ghatak Sitangshu Bhattacharya Debashis De Einstein Relation in Compound Semiconductors and Their Nanostructures With253 Figures 123 Professor Dr. Kamakhya Prasad Ghatak University of Calcutta, Department of Electronic Science Acharya Prafulla Chandra Rd. 92, 700 009 Kolkata, India E-mail: [email protected] Dr. Sitangshu Bhattacharya Nanoscale Device Research Laboratory Center for Electronics Design Technology Indian Institute of Science, Bangalore-560012, India E-mail: [email protected] Dr. Debashis De West Bengal University of Technology, Department of Computer Sciences and Engineering 700 064 Kolkata, India E-mail: [email protected] Series Editors: ProfessorRobertHull Professor Jürgen Parisi University of Virginia Universitat¨ Oldenburg, Fachbereich Physik Dept. of Materials Science and Engineering Abt. Energie- und Halbleiterforschung Thornton Hall Carl-von-Ossietzky-Strasse 9–11 Charlottesville, VA22903-2442, USA 26129 Oldenburg, Germany ProfessorR.M.Osgood,Jr. Professor Hans Warlimont Microelectronics Science Laboratory Institut fur¨ Festkorper-¨ Department of Electrical Engineering und Werkstofforschung, Columbia University Helmholtzstrasse 20 Seeley W. Mudd Building 01069 Dresden, Germany New York, NY 10027, USA Springer Series in Materials Science ISSN 0933-033X ISBN 978-3-540-79556-8 e-ISBN 978-3-540-79557-5 LibraryofCongressControlNumber:2008931052 © Springer-Verlag Berlin Heidelberg 2009 This work is subject to copyright. 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Typesetting: Data prepared by SPi using a Springer TEX macro package Cover concept: eStudio Calamar Steinen Cover production: WMX Design GmbH, Heidelberg SPIN: 12116942 57/3180/SPi Printed on acid-free paper 987654321 springer.com Preface In recent years, with the advent of fine line lithographical methods, molecular beam epitaxy, organometallic vapour phase epitaxy and other experimental techniques, low dimensional structures having quantum confinement in one, two and three dimensions (such as inversion layers, ultrathin films, nipi’s, quantum well superlattices, quantum wires, quantum wire superlattices, and quantum dots together with quantum confined structures aided by various other fields) have attracted much attention, not only for their potential in uncovering new phenomena in nanoscience, but also for their interesting applications in the realm of quantum effect devices. In ultrathin films, due to the reduction of symmetry in the wave–vector space, the motion of the carriers in the direction normal to the film becomes quantized leading to the quantum size effect. Such systems find extensive applications in quantum well lasers, field effect transistors, high speed digital networks and also in other low dimensional systems. In quantum wires, the carriers are quantized in two transverse directions and only one-dimensional motion of the carriers is allowed. The transport properties of charge carriers in quantum wires, which may be studied by utilizing the similarities with optical and microwave waveguides, are currently being investigated. Knowledge regarding these quantized structures may be gained from original research contributions in scientific journals, proceedings of international conferences and various re- view articles. It may be noted that the available books on semiconductor science and technology cannot cover even an entire chapter, excluding a few pages on the Einstein relation for the diffusivity to mobility ratio of the carriers in semiconductors (DMR). The DMR is more accurate than any one of the individual relations for the diffusivity (D) or the mobility (µ)ofthe charge carriers, which are two widely used quantities of carrier transport in semiconductors and their nanostructures. It is worth remarking that the performance of the electron devices at the device terminals and the speed of operation of modern switching transistors are significantly influenced by the degree of carrier degeneracy present in these devices. The simplest way of analyzing such devices, taking into account the VI Preface degeneracy of the bands, is to use the appropriate Einstein relation to express the performances at the device terminals and the switching speed in terms of carrier concentration (S.N. Mohammad, J. Phys. C , 13, 2685 (1980)). It is well known from the fundamental works of Landsberg (P.T. Landsberg, Proc. R. Soc. A, 213, 226, (1952); Eur. J. Phys, 2, 213, (1981)) that the Einstein relation for degenerate materials is essentially determined by their energy band structures. It has, therefore, different values in different materials having various band structures and varies with electron concentration, the magnitude of the reciprocal quantizing magnetic field, the quantizing electric field as in inversion layers, ultrathin films, quantum wires and with the superlattice period as in quantum confined semiconductor superlattices having various carrier energy spectra. This book is partially based on our on-going researches on the Einstein relation from 1980 and an attempt has been made to present a cross section of the Einstein relation for a wide range of materials with varying carrier energy spectra, under various physical conditions. In Chap. 1, after a brief introduction, the basic formulation of the Ein- stein relation for multiband semiconductors and suggestion of an experimental method for determining the Einstein relation in degenerate materials having arbitrary dispersion laws are presented. From this suggestion, one can also ex- perimentally determine another two seemingly different but important quantities of quantum effect devices namely, the Debye screening length and the carrier contribution to the elastic constants. In Chap. 2, the Einstein relation in bulk specimens of tetragonal materials (taking n-Cd3As2 and n-CdGeAs2 as examples) is formulated on the basis of a generalized electron dispersion law introducing the anisotropies of the effective electron masses and the spin orbit splitting constants respectively together with the inclusion of the crystal field splitting within the framework of the k.p formalism. The theoretical formulation is in good agreement with the suggested experimental method of determining the Einstein relation in degenerate materials having arbitrary dispersion laws. The results of III–V (e.g. InAs, InSb, GaAs, etc.), ternary (e.g. Hg1−xCdxTe), quaternary (e.g. In1−xGaxAs1−yPy lattice matched to InP) compounds

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