Welcome to our introduction to semiconductors. Semiconductors are fascinating materials that have electrical conductivity between conductors like metals and insulators like glass. On our conductivity scale, insulators like glass and rubber have very low conductivity, while conductors like copper and gold have very high conductivity. Semiconductors like silicon and germanium fall in the middle, which gives them unique properties that make them essential for modern electronics.
Let's explore the atomic structure of semiconductors. Materials like silicon have a crystalline structure where each atom forms covalent bonds with four neighboring atoms. Each silicon atom has four valence electrons that participate in these bonds. What makes semiconductors special is their variable conductivity. Unlike conductors or insulators, the conductivity of semiconductors can be significantly changed by factors like temperature, exposure to light, or by adding impurities through a process called doping. When heat is applied, some electrons can break free from their bonds, allowing current to flow.
Now let's explore semiconductor doping, which is the process of intentionally adding impurities to a semiconductor to change its electrical properties in a controlled way. There are two main types of doping. N-type doping involves adding atoms with five valence electrons, like phosphorus, to a semiconductor like silicon. The extra electron becomes free to move, creating a negative charge carrier. P-type doping involves adding atoms with three valence electrons, like boron. This creates 'holes' or electron vacancies that act as positive charge carriers. These two types of doped semiconductors are the building blocks for creating electronic components.
Semiconductors are the foundation of modern electronic components. Let's look at some key semiconductor devices. First, diodes are made from P-N junctions and allow current to flow in only one direction. They're used in power conversion and circuit protection. Transistors are semiconductor devices that can control the flow of current, acting as electronic switches or amplifiers. They're the fundamental building blocks of processors and memory. Integrated circuits, or ICs, combine many transistors and other components on a single chip. Modern processors can contain billions of transistors, enabling the complex electronic systems that power our digital world.
Let's summarize what we've learned about semiconductors. Semiconductors are materials with electrical conductivity between conductors and insulators. Their key property is that their conductivity can be controlled through temperature, light exposure, and doping. Doping creates two types of semiconductors: N-type with extra electrons and P-type with electron holes. These semiconductors are used to create devices like diodes, transistors, and integrated circuits that form the foundation of modern electronics. The development of semiconductor technology has driven remarkable progress in computing, communications, renewable energy, and medical devices. From the first transistor in 1947 to today's nanoscale devices and future quantum computing, semiconductors continue to revolutionize our world.