Semiconductor Fundamentals Unit 1 – Introduction to Semiconductors
UNIT 1 – INTRODUCTION TO SEMICONDUCTORS
UNIT OBJECTIVE
At the completion of this unit, you will be able to describe a semi-conductor, identify
semiconductor devices, and demonstrate their operation by using circuits on the
SEMICONDUCTOR DEVICES circuit board.
UNIT FUNDAMENTALS
Diodes, transistors, integrated circuits, and other so-called "solid state" devices are made from
crystals of a semiconductor material, usually silicon or germanium. At room temperature, the
crystals of pure silicon and germanium are neither good insulators nor good conductors. This is
why they are called semiconductors.
Introducing an impurity into a semiconductor crystal through doping reduces the electrical
resistance. Semiconductor material doped with impurities containing excess electrons is called N
type material (negative). If the impurity has too few valence ring electrons, the doped
semiconductor is called P type material (positive). Free electrons are the majority carriers in
N type material, and positive charges, called holes are the majority carriers in P type material.
Doping adjacent areas of a semiconductor crystal with N type and P type impurities,
respectively, forms a PN junction. In a region close to the junction, a few electrons migrate to
the P material and a few positive charges migrate to the N material. Because these migrated
charges tend to neutralize each other, an arrow depletion region is created.