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A semiconductor material has a resistivity lying between that of a conductor and that of an insulator. However, in contrast to the granular materials used for resistors, a semiconductor establishes its conduction properties through a complex quantum mechanical behavior within a periodic array of semiconductor atoms, i.e., within a crystalline structure. For appropriate atomic elements, the crystalline structure leads to a disallowed energy band between the energy level of electrons bound to the crystal's atoms and the energy level of electrons free to move within the crystalline structure (i.e., not bound to an atom) | Semiconductor Materials S. K. Tewksbury Microelectronic Systems Research Center Dept. of Electrical and Computer Engineering West Virginia University Morgantown WV 26506 304 293-6371 Sept. 21 1995 Contents 1 Introduction 2 2 Crystalline Structures 3 2.1 Basic Semiconductor Materials Groups. 3 2.1.1 Elemental IV-IV Semiconductors . 3 2.1.2 Compound III-V Semiconductors. 4 2.1.3 Compound II-VI Semiconductors. 6 2.2 Three-Dimensional Crystal Lattice . 6 2.3 Crystal Directions and Planes. 7 3 Energy Bands and Related Semiconductor Parameters 8 3.1 Conduction and Valence Band. 9 3.2 Direct Gap and Indirect Gap Semiconductors . 12 3.3 Effective Masses of Carriers . 13 3.4 Intrinsic Carrier Densities . 14 3.5 Substitutional Dopants. 16 4 Carrier Transport 18 4.1 Low Field Mobilities. 19 4.2 Saturated Carrier Velocities. 21 5 Crystalline Defects 23 5.1 Point Defects. 23 5.2 Line Defects. 24 5.3 Stacking Faults and Grain Boundaries . 26 5.4 Unintentional Impurities. 26 5.5 Surface Defects The Reconstructed Surface. 27 1 6 Summary 29 1 Introduction A semiconductor material has a resistivity lying between that of a conductor and that of an insulator. However in contrast to the granular materials used for resistors a semiconductor establishes its conduction properties through a complex quantum mechanical behavior within a periodic array of semiconductor atoms i.e. within a crystalline structure. For appropriate atomic elements the crystalline structure leads to a disallowed energy band between the energy level of electrons bound to the crystal s atoms and the energy level of electrons free to move within the crystalline structure i.e. not bound to an atom . This energy gap fundamentally impacts the mechanisms through which electrons associated with the crystal s atoms can become free and serve as conduction electrons. The resistivity of a semiconductor is proportional to the free carrier density and that density can be changed over a wide range by replacing a very small .