Introduction to Semiconductor Physics

Study Notes

Introduction to Semiconductor Physics

Semiconductors are materials with electrical conductivity between that of a conductor and an insulator.
Their conductivity can be modified substantially by adding impurities (doping), temperature changes, or exposure to light.
This property makes them crucial in modern electronics.

Intrinsic Semiconductors

Intrinsic semiconductors are pure, undoped materials.
Electrons in the valence band can become free electrons in the conduction band through thermal excitation.

Extrinsic Semiconductors

Extrinsic semiconductors are doped with impurities.
Doping creates either extra electrons (n-type) or electron "holes" (p-type).
N-type semiconductors have an excess of electrons.
P-type semiconductors have an excess of holes (missing electrons).

Energy Band Diagram

The energy band diagram illustrates the allowed energy levels for electrons in a material.
The valence band is the highest completely filled energy band.
The conduction band is the lowest partially filled or empty energy band.
The energy gap (bandgap) separates the valence and conduction bands.
The bandgap energy determines the material's electrical conductivity.

Carrier Concentrations

The number of free electrons and holes in a semiconductor is described by carrier concentrations.
These are influenced by temperature and doping concentration.
Equilibrium carrier concentrations exist under stable conditions.
Non-equilibrium carrier concentrations occur when external factors, like light or electric fields, disrupt the balance.

Doping Effects

Doping with impurities can significantly alter the conductivity of semiconductors.
Different doping concentrations create different levels of n-type or p-type conductivity.
The doping level is critical to controlling the electrical properties of the semiconductor.

PN Junctions

A PN junction is formed by the contact of p-type and n-type semiconductors.
A depletion region forms at the junction, containing immobile ions.
The depletion region acts as a barrier to current flow.
PN junctions behave as diodes, allowing current in one direction only.

Semiconductor Devices

Semiconductors are the basis for most modern electronic devices.
Diodes, transistors, integrated circuits are examples of semiconductor devices.
Diodes rectify alternating current.
Transistors amplify or switch electronic signals.
Integrated circuits (ICs) contain many transistors and other components on a single chip.

Impact of Temperature

Increased temperature increases the number of free electrons and holes, increasing conductivity.
At higher temperatures, the conductivity rises exponentially.

Impact of Light

Light with sufficient energy can excite electrons from the valence band to the conduction band, increasing the conductivity (photoconductivity).
This effect is used in photodetectors.

Types of Semiconductor Materials

Silicon (Si) and Germanium (Ge) are common examples.
Other materials, like Gallium Arsenide (GaAs), have specific applications due to their unique properties.

Applications of Semiconductors

Microprocessors, memory chips, LEDs, solar cells, and many other modern technologies.
Semiconductors are ubiquitous in modern electronics.

Description

This quiz covers fundamental concepts in semiconductor physics, including intrinsic and extrinsic semiconductors. Understand the differences between n-type and p-type materials, and explore energy band diagrams. Perfect for students delving into the basics of electronics and material science.