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

1. Lecture 2
Chapter 1
The Crystal Structure of Solids

2. Preview

Our interest : electrical properties and
characteristics of semiconductor materials and
devices.

Electrical properties of a single­crystal 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, AlxGa1­xAs

Quaternary (four element) : InGaAsP

5. TYPES OF SOLIDS
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.
Amorphous Polycrystalline
Single Crystal

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.

Single­crystal materials, ideally, have a high
degree of order, or regular geometric
periodicity, throughout the entire volume of the
material.

The single­crystal regions are called grains and
are separated from one another by grain
boundaries.

Advantage of a single­crystal material: superior

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

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

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
1.Find the intercepts of the plane with the crystal axes and express
those intercepts as integral multiples of the basis vectors.
2.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.
3.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