Key Terms Flashcards
Band Gap
Band gap is an energy range in a solid where no electronic states can exist. This means that electrons cannot move from one energy level to another within this range. The band gap is a fundamental property of semiconductors and insulators, and it determines their electrical properties.
The band gap is caused by the interaction of the electrons in a solid with the periodic potential of the crystal lattice. The periodic potential creates a series of energy levels for the electrons, called energy bands. The band gap is the energy difference between the highest energy level in the valence band and the lowest energy level in the conduction band.
In semiconductors, the band gap is relatively small, so electrons can be excited from the valence band to the conduction band by absorbing energy from a photon or from thermal energy. This allows electrons to move freely in the conduction band, which is responsible for the electrical conductivity of semiconductors.
In insulators, the band gap is much larger, so it is much more difficult to excite electrons from the valence band to the conduction band. This makes insulators poor conductors of electricity.
The band gap is an important property of semiconductors and insulators, and it is used to determine their electrical properties. The band gap can be measured using a variety of techniques, including optical spectroscopy and electrical measurements.
Here are some of the applications of band gap:
Semiconductors: The band gap of a semiconductor determines its electrical conductivity. Semiconductors with a small band gap, such as silicon and germanium, are used to make transistors and integrated circuits.
Insulators: Insulators with a large band gap, such as silicon dioxide and mica, are used to make electrical insulation and capacitors.
Solar cells: Solar cells convert sunlight into electricity. The band gap of the semiconductor in a solar cell determines the wavelength of light that the solar cell can absorb.
Light-emitting diodes (LEDs): LEDs emit light when electrons are excited from the valence band to the conduction band. The band gap of the semiconductor in an LED determines the color of light that the LED emits.
The band gap is a fundamental property of semiconductors and insulators, and it is used in a wide variety of applications.
Conductivity:
The conductivity of a semiconductor is a measure of its ability to conduct electricity. It is determined by the band gap, the temperature, and the doping level of the semiconductor.
Doping
Doping is the process of adding impurities to a semiconductor to change its electrical properties. Doping can increase or decrease the conductivity of a semiconductor.
The amount of current that flows through a semiconductor can be controlled by the doping level. Doping is the process of adding impurities to a semiconductor to change its electrical properties. Doping can increase or decrease the number of electrons and holes in the semiconductor, which changes the conductivity of the semiconductor.
Carrier concentration
The carrier concentration is the number of electrons and holes in a semiconductor. It is determined by the doping level and the temperature of the semiconductor.
Mobility
The mobility of a carrier is a measure of its ability to move through a semiconductor. It is determined by the type of semiconductor and the temperature.
Resistivity
the resistivity of a semiconductor is a measure of its resistance to the flow of electricity. It is determined by the conductivity, the carrier concentration, and the mobility of the carriers.
Valence and conductive bands
The valence band is the band of electrons that are bound to the atoms of the semiconductor. The conduction band is the band of electrons that are free to move around.
Flow of electrons
When an electron is excited, it can jump from the valence band to the conduction band. This leaves a hole in the valence band, which can be filled by another electron. The flow of electrons and holes is what allows electricity to flow through a semiconductor.
Semiconductor
A material that has electrical conductivity intermediate between that of a conductor and an insulator. Semiconductors are used in a wide variety of electronic devices, including transistors, diodes, and integrated circuits.
Intrinsic semiconductor
A pure semiconductor that has no impurities added to it. Intrinsic semiconductors have a small band gap, which means that they can be easily excited into the conduction band.
Extrinsic semiconductor
A semiconductor that has impurities added to it. The impurities can either be donors, which add electrons to the conduction band, or acceptors, which remove electrons from the valence band. This changes the band gap of the semiconductor and makes it easier to excite electrons into the conduction band.
Band gap
The energy difference between the valence band and the conduction band in a semiconductor. The band gap determines the conductivity of the semiconductor.
Valence band
The band of electrons that are tightly bound to the atoms in a semiconductor.
Conduction band
The band of electrons that are free to move around in a semiconductor.
Doping
The process of adding impurities to a semiconductor to change its properties.
