Semiconductors

We explain what an electrical semiconductor is, its types, applications and examples. In addition, conductive and insulating materials.

electrical semiconductor silicon integrated circuit
The most used semiconductor is silicon.

What is a semiconductor?

Semiconductors are materials capable of acting as electrical conductors or as electrical insulators depending on the physical conditions in which they are found. These conditions usually involve temperature and pressure, the incidence of radiation or the intensities of the electric field or magnetic field to which the material is subjected.

Semiconductors are composed of very varied chemical elements, which in fact come from different regions of the Periodic Table, but which share certain chemical traits (generally they are tetravalent), which give them their particular electrical properties. Currently, The most used semiconductor is silicon (Si) particularly in the electronics and computing industry.

Along with insulating materials, semiconductors were discovered in 1727 by the English physicist and naturalist Stephen Gray (1666-1736), but the laws that describe their behaviors and properties were described much later, in 1821, by the famous German physicist Georg Simon Ohm (1789-1854).

Also: Properties of matter

Semiconductor applications

Semiconductors are especially useful in the electronics industry since they allow the electrical current to be conducted and modulated according to the necessary patterns. For this reason, it is common for them to be used to:

  • Transistors
  • integrated circuits
  • electrical diodes
  • Optical sensors
  • Solid state lasers
  • Electrical drive modulators (such as an electric guitar amplifier)
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Types of semiconductors

Semiconductors can be of two different types, depending on their response to the physical environment in which they are found:

Intrinsic Semiconductors

They are made up of a single type of atoms, arranged in tetrahedral molecules (that is, four atoms with a valence of 4) and their atoms joined by covalent bonds.

This chemical configuration prevents the free movement of electrons around the molecule, except when the temperature increases: then the electrons take part of the available energy and “jump”, leaving a free space that translates as a positive charge, which in turn it will attract new electrons. This process is called recombination, and the amount of heat required for this depends on the chemical element in question.

Extrinsic semiconductors

These materials allow a doping process that is, they allow some type of impurities to be included in their atomic configuration. Depending on these impurities, which can be serpentavalent or trivalent, semiconductor materials are divided into two:

  • Extrinsic N-type semiconductors (donor). In this type of materials, electrons outnumber holes or free charge carriers (“spaces” of positive charge). When a potential difference is applied to the material, the free electrons move to the left of the material and the holes then move to the right. When the holes reach the right end, the electrons from the external circuit enter the semiconductor, and the transmission of electric current occurs.
  • P-type extrinsic semiconductors (acceptors). In these materials, the added impurity, instead of increasing the available electrons, increases the holes. Thus, we speak of added acceptor material, since there is a greater demand for electrons than availability and each free “space” where an electron should go serves to facilitate the passage of current.
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Examples of semiconductor materials

semiconductor electrical amplifier
Semiconductors serve as electrical transmission modulators.

The most common semiconductors used in the industry are:

  • Silicon (Yes)
  • Germanium (Ge), often in silicon alloys
  • Gallium Arsenide (GaAs)
  • Sulfur
  • Oxygen
  • Cadmium
  • Selenium
  • Indian
  • Other chemical materials resulting from the combination of elements from groups 12 and 13 of the periodic table, with elements from groups 16 and 15 respectively.

Conductive materials

Unlike semiconductors, whose electrical conduction properties vary, conductive materials are always ready to transmit electricity due to the electronic configuration of its atoms. This conductivity can oscillate and be affected to a certain degree by the physical state of the environment since electrical conductivity is not absolute.

Examples of conductive materials are the vast majority of metals (iron, mercury, copper, aluminum, etc.) and water.

Insulating materials

Finally, insulating materials are those that resist the conduction of electricity that is, they prevent the passage of electrons and are useful, therefore, to protect against electricity, to prevent it from following a free course, or from causing short circuits. Insulators do not insulate 100% efficiently either. They have a limit (breakdown voltage) beyond which the energy is so intense that they cannot maintain their condition as insulators and, therefore, transmit the electric current, at least in certain degree.

Examples of insulating materials are plastic, ceramics, glass, wood and paper.

References

  • “Semiconductor” on Wikipedia.
  • “Semiconductors” at the University School of Industrial Technical Engineering (Spain).
  • “What is a semiconductor? A simple explanation” (video) on MindMachineTV.
  • “Properties of semiconductor and conductive materials” (video) in CienciaMX.
  • “Semiconductor introduction” (video) on Khan Academy.
  • “Semiconductor (electronics)” in The Encyclopaedia Britannica.
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