Chapter 3 - Semiconductor electronic devices

Abstract

This chapter discusses the semiconductor electronic devices' basic principle of functionality. First, it describes how covalent bonds and doping materials impact on semiconductor electronic devices. By controlling the amounts of doping materials, it is possible to affect the density of holes and excess electrons. The doped material is called an n-type semiconductor (excess of electrons) and a p-type (deficit of electrons) semiconductor. When external energy (electrical, heat, or light) is applied to n-type semiconductor material, the excess electrons are made to wander through the material: the negative terminal of the applied potential repulses the free electrons and the positive terminal attracts the free electrons. A diode can be formed by joining a p-type and n-type semiconductor together. The behavior of a diode depends on the polarity of the source of potential energy connected to it. If the diode is reverse biased (positive potential on n-type material), the depletion layer increases. The only charge carriers that are able to support a net current across the p-n junction are the minority carriers, and hence, the reverse current is very small. A forward-biased diode (positive potential on p-type material) has a decreased depletion region; the majority carriers can diffuse across the junction. There are several other types of diodes such as junction and zener diode. In a zener diode, as the reverse voltage increases, the diode can reach the avalanche breakdown (Zener breakdown) condition. This causes an increase in current in the reverse direction, which makes it applicable in voltage regulators.