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Introduction to Semiconductors

• Semiconductors: Materials that have electrical conductivity between conductors and insulators. They are fundamental to modern electronics.

Types of Semiconductors

• Intrinsic Semiconductors: Pure semiconductors without any impurity. Examples include silicon (Si) and germanium (Ge). They have a balanced number of charge carriers (electrons and holes).

• Extrinsic Semiconductors: Doped semiconductors that have added impurities to change their electrical properties. They can be categorized into two types:

  • n-type Semiconductors: Created by doping intrinsic semiconductors with donor atoms that provide extra electrons, improving conductivity.

  • p-type Semiconductors: Formed by doping with acceptor atoms, creating holes (positively charged spaces) that assist charge transfer.

Charge Carriers

• Electrons are negatively charged carriers.

• Holes are the absence of electrons and behave like positively charged particles. They are considered as charge carriers in p-type semiconductors.

Doping Process

• Doping: The introduction of impurities into a semiconductor to modify its electrical properties. Donor atoms contribute free electrons, while acceptor atoms create holes.

• Donor Atoms: Elements such as phosphorus in silicon that provide extra electrons.

• Acceptor Atoms: Elements such as boron in silicon that create holes.

Depletion Layer

• A region in a semiconductor diode where mobile charge carriers (electrons and holes) are depleted, creating a region under an electric field that barriers current flow unless enough voltage is applied.

Diodes and Rectification

• Diode: A semiconductor device that allows current to flow in one direction. They are critical in converting alternating current (AC) to direct current (DC).

• Rectifier Diode: Specialized type used for rectifying AC to DC.

• Bridge Rectifier: Circuit using four diodes arranged intelligently to convert AC into DC efficiently.

Light Emitting Diodes (LEDs)

• LED: A diode that emits light when current flows through it. They are vital in-display technologies and lighting applications.

Transistors

• Transistor: A semiconductor device used to amplify or switch electronic signals. It consists of three parts: collector, emitter, and base.

Amplifiers

• Current Amplifier: A circuit that increases the current of a signal without altering its voltage.

• Signal Amplifier: Similar to current amplifiers, they boost the strength of a signal to drive loads more effectively.

Biasing in Semiconductors

• Forward Bias: Connecting the positive terminal of a voltage source to the p-type material and the negative to the n-type allowing current to flow easily through the junction.

• Reverse Bias: Connecting the opposite terminals to inhibit current flow, wide application in power supply systems for controlling current.