Semiconductor Materials

Introduction

• Semiconductor materials are a crucial class of materials used extensively in electronics and technology.
• Key semiconductor elements include silicon and germanium, both of which have unique properties that make them suitable for electronic applications.

Four Outer Shell Electrons

• Silicon and germanium are semiconductors due to their atomic structure.
• These elements have four outer shell electrons, allowing them to form four covalent bonds with other identical atoms.
• This property enables them to create a crystalline structure with strong covalent bonds.

Pure Silicon Crystal

• In a pure silicon crystal, each silicon atom is surrounded by four other silicon atoms, forming a tetrahedral structure.
• The strong covalent bonds between silicon atoms make the crystal an insulator, as there are no free charge carriers to conduct electricity.

Doping Process

• To make silicon or germanium suitable for electronic applications, they are doped with small quantities of impurities.
• Doping involves introducing specific impurities into the crystal lattice by diffusing them as gases during the crystallisation process.
• The two common types of doping are:
  • N-Type: Introduces elements with five outer shell electrons, creating an excess of free electrons (negative charge carriers).
  • P-Type: Introduces elements with three outer shell electrons, creating "holes" or spaces in the crystal lattice where electrons can move (positive charge carriers).
• Doping significantly alters the semiconductor's electrical properties and conductivity.

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Semiconductor Materials

P-N Junction Diode

• One essential semiconductor device is the p-n junction diode.
• It consists of a p-type and an n-type semiconductor connected together.
• The p-n junction creates a region where charge carriers (electrons and holes) can recombine, allowing the controlled flow of current in one direction.
• P-n junction diodes are fundamental building blocks in electronic circuits.

Key Points

• Silicon and germanium are semiconductors due to their atomic structure with four outer shell electrons.
• Pure silicon forms a crystalline lattice with strong covalent bonds and is initially an insulator.
• Doping involves introducing specific impurities into the crystal lattice to create charge carriers, enabling electrical conductivity.
• N-type doping introduces free electrons, while p-type doping creates "holes."
• The combination of p-type and n-type semiconductors forms p-n junction diodes, essential for electronics.

Summary

• Semiconductor materials like silicon and germanium are fundamental in modern electronics. Their ability to be doped and control the flow of charge carriers makes them versatile for various applications, from transistors to diodes.