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Ete411 Lec2

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Lecture on Introduction of Semiconductor at North South University as the undergraduate course (ETE411) …

Lecture on Introduction of Semiconductor at North South University as the undergraduate course (ETE411)
=======================
Dr. Mashiur Rahman
Assistant Professor
Dept. of Electrical Engineering and Computer Science
North South University, Dhaka, Bangladesh
http://mashiur.biggani.org

Published in: Technology, Sports

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  • 1. Chapter 1 The Crystal Structure of Solids Lecture 2
  • 2. Preview
    • Our interest : electrical properties and characteristics of semiconductor materials and devices.
    • Electrical properties of a single-crystal material are determined not only by the chemical composition but also by the arrangement of atoms in the solid.
  • 3. SEMICONDUCTOR MATERIALS
  • 4. Compound semiconductor
    • Binary (two element): GaN, GaP, GaAs
    • Ternary (three element) : GaAsP, Al x Ga 1-x As
    • Quaternary (four element) : InGaAsP
  • 5. TYPES OF SOLIDS Amorphous Polycrystalline Single Crystal Characterized by the size of an ordered region within the material. Ordered region is a spatial volume in which atoms or molecules have a regular geometric arrangement or periodicity.
  • 6.
    • Amorphous materials have order only within a few atomic or molecular dimensions,
    • Polycrystalline materials have a high degree of order over many atomic or molecular dimensions.
    • Single-crystal materials , ideally, have a high degree of order, or regular geometric periodicity, throughout the entire volume of the material.
    • The single-crystal regions are called grains and are separated from one another by grain boundaries .
    • Advantage of a single-crystal material: superior electrical properties.
  • 7. SPACE LATTICES
    • A representative unit, or group of atoms, is repeated at regular intervals in each of the three dimensions to form the single crystal. The periodic arrangement of atoms in the crystal is called the lattice .
    • We can represent a particular atomic array by a dot that is called a lattice point .
    • A unit cell is a small volume of the crystal that can be used to reproduce the entire crystal
  • 8.  
  • 9. Where p, q, and s are integers. Since the location of the origin is arbitrary, we will let p. q, and s be positive integers for simplicity.
  • 10. Basic Crystal Structures
  • 11.  
  • 12. Exercise
  • 13. Crystal Planes and Miller Indices
    • Since real crystals are not infinitely large, they eventually terminate at a surface. Semiconductor devices are fabricated at or near a surface, so the surface properties may influence the device characteristics.
  • 14. Planes and Directions
    • Find the intercepts of the plane with the crystal axes and express those intercepts as integral multiples of the basis vectors.
    • Take the reciprocals of the three integers found in step 1 and reduce these to smallest set of integers h , k and l , which have the same relationship to each other as the three reciprocals.
    • Label the plane (hkl)
    • The three integers h , k and l are called Miller indices.
    • If an intercepts occurs on the negative branch of an asix, the minus sign is placed above the Miller index for convenience, such as
  • 15.  
  • 16.