1.01 Semiconductor Theory

Introduction
There are three basic types of materials that we are concerned with in electronics. These are conductors, semiconductors and insulators.
Materials that have very low electrical resistivity (in the order of 1 x 10-6 ohm-metres) are called conductors.
Materials that have very high electrical resistivity (in the order of 1 x 1013 ohm-metres) are called insulators.
Semiconductors have resistivity values in between those of conductors and insulators, they are neither good conductors nor good insulators.

Examples of conductors:
  • Copper
  • Aluminium
  • Silver
  • Gold
Examples of insulators:
  • Rubber
  • PVC
  • Paper
  • Mica
Examples of Semiconductors:
  • Silicon
  • Germanium

Modern electronic components are made from Semiconductor. In order to understand how these devices work we need to understand the electrical properties of naturally occurring (or intrinsic) semiconductor material. We then need to understand how this material is modified to produce what is called extrinsic semiconductor material and how this effects its electrical properties.

Firstly we will examine the atomic structure of intrinsic semiconductor and how this relates to its natural conduction properties. Then we will look at how this structure is modified to produce extrinsic semiconductor and how this changes the materials electrical properties. We will then go on to look at how electronic component are made using P and N type semiconductor starting with the most basic component, the semiconductor diode.