Semiconductor Devices (Diodes, Transistors) - SS3 Physics Lesson Note

Semiconductor devices are electronic components that are made from semiconducting materials, such as silicon or germanium. These devices are used extensively in modern electronics and have revolutionized the field of electronics.

Two of the most important semiconductor devices are diodes and transistors.

A diode is a two-terminal electronic component that conducts electric current in only one direction. It has a p-n junction, which is formed by doping one side of a semiconductor crystal with impurities that create a surplus of electrons (n-type) and the other side with impurities that create a deficiency of electrons (p-type). When a voltage is applied to the diode in the forward direction, the surplus electrons in the n-type material combine with the deficiencies in the p-type material, allowing electric current to flow. However, in the reverse direction, the surplus electrons and deficiencies are forced apart, creating a high resistance to current flow.

A transistor is a three-terminal electronic device that can amplify or switch electronic signals. It consists of a sandwich of p-type and n-type semiconducting materials, with two junctions between them. The three terminals are called the emitter, base, and collector. The current flowing between the emitter and collector is controlled by the voltage applied to the base. In this way, a small current can be used to control a much larger current, making transistors useful in a wide range of applications, from simple amplifiers to complex digital circuits.

Semiconductor devices have many practical applications, including in computers, televisions, cell phones, and other electronic devices. They are also used in a variety of industrial and scientific applications, such as sensors, detectors, and power controllers.