Semiconductor Devices
Semiconductors, whether inorganic or organic, are materials with a unique ability to control their conduction. This control is influenced by their chemical structure, temperature, illumination, and the presence of dopants. The term „semiconductor“ derives from their electrical conductivity, which lies between that of a metal (such as copper or gold) and an insulator (like glass). They possess an energy gap of less than 4eV (approximately 1eV).
In solid-state physics, this energy gap, or band gap, represents the energy range between the valence band and conduction band where electron states are forbidden. Unlike conductors, in semiconductors, electrons require energy, for example, from ionizing radiation, to cross the band gap and reach the conduction band. The distinct properties of semiconductors are primarily determined by this energy gap.
Semiconductor Devices
Semiconductor devices are electronic components created from semiconductor materials, such as silicon. These devices exhibit electrical properties that are intermediate between those of conductors and insulators. Common semiconductor devices include:
- Diodes: A diode is a two-terminal electronic component that allows current flow in only one direction. It comprises a p-type semiconductor (with an excess of holes) and an n-type semiconductor (with an excess of electrons).
- Transistors: These three-terminal devices can amplify or switch electronic signals. They are made by joining three layers of semiconductor material: an n-type layer, a p-type layer, and another n-type or p-type layer, depending on whether it’s an NPN or PNP transistor.
- Integrated Circuits (ICs): ICs are miniaturized electronic circuits combining multiple semiconductor devices like diodes, transistors, and resistors on a single silicon piece. They are used in various electronic devices, from computers to automobiles.
- Solar Cells: These devices convert sunlight into electricity using a silicon wafer doped to create p-type and n-type regions, which generates a voltage through the separation of electrons and holes.
- Light-Emitting Diodes (LEDs): LEDs are semiconductor devices that emit light when current flows through them. They are created by doping semiconductor material to create a p-n junction, which emits light when electrical current passes.
Types of Semiconductors
Semiconductors are broadly classified into two categories:
- Intrinsic Semiconductors: These are pure semiconductors, like Silicon or Germanium, without intentional doping. They conduct electricity when heated, allowing some electrons to gain enough energy to move to the conduction band.
- Extrinsic Semiconductors: These are doped with impurities to modify their electronic properties and are of two types:
- p-type Semiconductors: In these, impurity atoms like boron create „holes“ in the valence band, acting as positive charge carriers.
- n-type Semiconductors: Here, impurities like phosphorus add extra electrons in the conduction band, acting as negative charge carriers.
Each type of semiconductor has unique characteristics that are exploited in various electronic applications, making them essential components in modern technology.
