Key Notes On Semiconductors

Semiconductors are materials with conductivity halfway between conductors, which are generally metals, and nonconductors or insulators, which are usually ceramics. Semiconductors can be compounds such as gallium phosphide or pure elements such as germanium or silicon. The ideas, characteristics, and mathematical techniques that control semiconductors are explained in physics.

Semiconductors include the following:

Some of the most prevalent semiconductors include gallium arsenide, germanium, and silicon. Silicon is employed in the manufacturing of electrical circuits, whereas gallium arsenide is being used in solar panels, laser diodes, and other applications.

Semiconductors’ Holes and Electrons

In semiconductors, the charge carriers responsible for current flow are holes and electrons. Holes (valence electrons) are positively charged electrically charged carriers, whereas electrons are negatively charged. Electrons and holes have the same magnitude but opposite polarity.

Electron and Hole Mobility

The electron mobility in a semiconductor is greater than that of holes. It is mostly due to their distinct band structures and dispersing processes.

Electrons move via the conduction band, whereas holes move through the valence band. Because of their limited mobility, holes cannot travel as easily as electrons in an electric field. Elevating electrons from their subshell to higher shells causes holes to form in semiconductors. Because the nucleus exerts a larger atomic force on holes than on electrons, holes have poorer mobility.

A particle’s mobility in a semiconductor is increased if;

Particles have a lower effective mass.

There is a long time between scattering occurrences.

At 300 K, the electron mobility is 1500 cm2 (Vs)-1 and that of vacancies is 475 cm2 (Vs)-1 for intrinsic silicon.

The electron bond model in silicon of valence state 4 is presented below. When one of the unpaired electrons (blue dots) departs the lattice location, a hole is formed (grey dots). This hole so formed has the opposite polarity of the electron and can be seen as positive charge carriers travelling across the lattice.

Semiconductor Characteristics

Under favourable settings or situations, semiconductors may conduct electricity. Because of this one-of-a-kind feature, It is an excellent substance for carrying electricity in a controlled manner as required.

Unlike conductors, electric charges in semiconductors originate only as a function of environmental energy, namely thermal agitation. It causes a specific amount of electrons to bridge the energy gap and enter the conduction band, resulting in a proportional number of empty energy states. Conduction caused by electrons is important.

Semiconductors have the following important properties:

A semiconductor acts as an insulator at zero Kelvin. When the temperature rises, it functions as a conductor.

Because of their outstanding electrical characteristics, semiconductors may be fixed to create semiconductor devices appropriate for energy transfer, amplifiers, and switches.

Less power is dissipated.

Semiconductors are smaller in size and lighter in weight, when compared to a transistor.

Their permeability is higher than that of conductors but lower than that of insulators.

The impedance of semiconductor devices lowers as temperature rises and vice versa.

Semiconductor Types

Semiconductors are classed as follows:

·   Semiconductor Intrinsic

·   Semiconductor Extrinsic

Semiconductor Intrinsic

Chemically, an intrinsic semiconductor material is created to be exceedingly pure. It is composed of only one sort of constituent.

Germanium (Ge) and silicon are the most common inherent semiconductor elements (Si). Their valence shell has four electrons (tetravalent). They are bound together by a covalent bond at absolute zero temperatures.

When the temperature rises due to collisions, a few electrons become unbound and free to wander about the lattice, causing an absence in its initial site (hole). These unbound electrons and holes aid in the transmission of energy in the semiconductor. There are an equal number of negative charge carriers and positive charge carriers.

Few atoms in the structure can be ionised by thermal energy, which can lead to lower conductivity.

The Pure Silicon Semiconductor Lattice at Different Temperatures

The temperature at absolute zero Kelvin: The covalent bonds are exceptionally strong at this temperature, there have been no free electrons, and the semiconductor functions as a perfect insulator.

In excess of absolute zero: As the temperature rises, a few valence electrons enter the conduction band, causing it to act as a poor conductor.

Semiconductor Extrinsic

The conductivity of semiconductors can be significantly improved by introducing a limited number of appropriate replacement atoms known as IMPURITIES. The technique of familiarising impure atoms with a pure semiconductor is known as DOPING. Only one atom out of every 107 in a doped semiconductor is replaced by a dopant atom. Extrinsic semiconductors are classified again as follows:

·   Semiconductor of the N-type

·   Semiconductor of the P-type

 Semiconductor Applications

Now consider how semiconductors are employed in everyday life. Semiconductors may be found in almost every electrical device. If they didn’t exist, our daily lives would be quite different.

Because of their durability, compactness, low cost, and controlled electrical conduction, they are ideal for use in a wide range of materials and systems. Semiconductors are used in the manufacture of semiconductors, microcontrollers, diodes, photosensors,  integrated circuits, and a variety of other devices.

Semiconductors’ Applications in Everyday Life

• Temperature sensors are made with semiconductors.
• They are often found in 3D printers.
• It is used in computer chips and self-driving automobiles.
• It is used in calculators, computers, solar plates, and other electrical devices.
• Semiconductors are used in the fabrication of transistors and MOSFETs, which are used as switches in electrical circuits.

Semiconductor Applications in Industry

Semiconductors’ physical and chemical properties enable them to be utilised to build technological wonders such as microchips, transistors, LEDs, solar cells, and so on.

The microprocessor, which is used to regulate the functioning of space vehicles, railroads, and robots, is made up of transistors and other regulating devices created from semiconductor materials.