Semiconductors
Semiconductors are materials which have electrical conductivity between that of conductors (like metals) and insulators (like ceramics). Their ability to control electrical current makes them fundamental to modern electronics, including devices like computers, smartphones, and solar panels.
History
The study of semiconductors began with the discovery of the photoelectric effect in 1839 by Alexandre Edmond Becquerel. However, the real breakthrough came in the 20th century:
- 1907: H.J. Round created the first LED, although it was not recognized at the time.
- 1947: Transistors were invented at Bell Laboratories by William Shockley, John Bardeen, and Walter Brattain. This invention led to the replacement of vacuum tubes with more efficient and smaller devices.
- 1958: Jack Kilby of Texas Instruments developed the first integrated circuit, laying the groundwork for microelectronics.
- 1960s-1970s: The development of silicon wafers and photolithography techniques allowed for the mass production of semiconductors.
- 1980s onwards: Advancements in materials science and nanofabrication led to the creation of more complex and efficient semiconductor devices.
Properties
- Band Gap: Semiconductors have a band gap that allows them to conduct electricity only under certain conditions. This can be manipulated by doping with impurities.
- Doping: The process of intentionally introducing impurities into an extremely pure semiconductor to change its electrical properties.
- P-N Junctions: When a p-type (positive) semiconductor is joined with an n-type (negative) semiconductor, it forms a p-n junction which can act as a diode or transistor.
Types of Semiconductors
- Elemental Semiconductors: Materials like silicon and germanium.
- Compound Semiconductors: Such as gallium arsenide (GaAs), which offer advantages like higher electron mobility.
- Organic Semiconductors: Carbon-based materials used in flexible electronics and solar cells.
- Amorphous Semiconductors: Materials with no long-range order, like amorphous silicon used in thin-film transistors.
Applications
- Integrated Circuits (ICs): The backbone of digital electronics, enabling the miniaturization of electronic devices.
- Photovoltaics: Solar cells use semiconductors to convert sunlight into electricity.
- LEDs: Light-emitting diodes, which are energy-efficient light sources.
- Power Electronics: High-power switches in electric vehicles and power supplies.
Manufacturing Process
The creation of semiconductor devices involves several steps:
- Crystal Growth: Growing single-crystal ingots of silicon or other semiconductor materials.
- Wafer Production: Slicing the ingot into thin wafers.
- Photolithography: Using light to transfer geometric patterns from a photomask to the wafer's surface.
- Etching: Removing unwanted material from the wafer to create the device structure.
- Doping: Introducing impurities to alter the semiconductor's electrical properties.
- Deposition: Adding layers of material to the wafer.
- Assembly and Testing: Packaging the semiconductor chips into their final forms and testing for functionality.
Sources
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