tags: essay, chemistry, circuits
Society is filled to the brim with a plethora of electrical devices, such as computers, phones, and even simple calculators. Such technology is made possible through the application of semiconductor materials. A semiconductor is a material that has an electrical conductivity that lies between that of an electrical conductor (mainly metals, such as copper and aluminum) and an electrical insulator (such as rubber or wood), with the most common semiconductor materials being silicon and germanium. Semiconductor materials operate on two main principles: bandgap and doping. 1
Everything in the universe is composed of atoms. Atoms have electron orbitals, also known as shells which can be thought of as the “path” that an electron takes when orbiting around the atoms’ nucleus. When atoms combine on the macroscopic level, the shells combine together to form bands. The filled, lower energy orbitals are known as the valence band. Electrons in the valence band are still bound too strongly to their atoms’ nucleus, and can not conduct an electric current. The empty, higher energy orbitals are known as the conduction bands. The electrons, when in the conduction bands, require little energy to move freely and can conduct an electric current. The distance between the valence band and the conduction band is known as the material’s bandgap, and is responsible for a material’s conductivity. Electrically resistant materials have a very high bandgap, while electrically conductive materials have a very low bandgap. Semiconductive materials have a bandgap that lies between that of a resistor and a conductor, so adding energy to the system (e.g. heating) allows the electrons to more easily move to the conduction band. It is the ability to control the material’s conductivity that gives semiconductors their utility.1 2
The second major principle of semiconductors is doping. Doping is the act of adding tiny amounts of impurities to the material in order to improve its quality. A “perfect” semiconductor is not as efficient or useful as an impure one as the distance between the valence band and the conduction band may still require too much energy to conduct electricity easily. The impurities are incorporated into the crystalline structure of the material, and with it, bring more electrons. These electrons fill the valence bands, forcing the “extra” electrons into a donor band, which is much closer to the conduction band, requiring less energy for electrons to move to the conduction band. 2 3 Impurities can also arrive unintentionally either as an intrinsic trait of the material or through manufacturing.. Being able to control which impurities are added is key to producing effective and lasting semiconductors. 4
Semiconductor materials have seen an increased usage since their inception and have proven to have practical applications. The ability to finely control the material’s conductivity has seen use in many of the devices that are used nowadays, such as transistors and integrated circuits.2 Efforts in semiconductor research are currently studying the effects of different doping compounds as well as more efficient means of production.3
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