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A semiconductor material has an electrical conductivity value falling between that of a conductor, such as copper, and an insulator, such as glass. Semiconductors are the foundation of modern electronics. Semiconducting materials exist in two types - elemental materials and compound materials.[1] The modern understanding of the properties of a semiconductor relies on quantum physics to explain the movement of electrons and holes in a crystal lattice.[2] The unique arrangement of the crystal lattice makes silicon and germanium the most commonly used elements in the preparation of semiconducting materials. An increased knowledge of semiconductor materials and fabrication processes has made possible continuing increases in the complexity and speed of microprocessors and memory devices. Some of the information on this page may be outdated within a year because new discoveries are made in the field frequently.[2]



Some of the properties of semiconductor materials were observed throughout the mid 19th and first decades of the 20th century. Development of quantum physics in turn allowed the development of the transistor in 1947.[3] Although some pure elements and many compounds display semiconductor properties, silicon, germanium, and compounds of gallium are the most widely used in electronic devices. Elements near the so-called "metalloid staircase", where the metalloids are located on the periodic table, are usually used as semiconductors.

The nickname of the southern area of Northern California is Silicon Valley because of all the influential tech companies that have their headquarters there. An integral part of today’s technology is built upon semiconductors, which are made primarily of silicon. Some major companies include Marvell Technology Group, National Semiconductor (now part of Texas Instruments), and Advanced Micro Devices.[4]


Variable conductivity
Semiconductors in their natural state are poor conductors because a current requires the flow of electrons, and semiconductors have their valence bands filled. There are several developed techniques that allows semiconducting materials to behave like conducting materials, such as doping or gating. These modifications have two outcomes: n-type and p-type. These refer to the excess or shortage of electrons, respectively. An unbalanced number of electrons would cause a current to flow through the material.[1]
Heterojunctions occur when two differently doped semiconducting materials are joined together. For example, a configuration could consist of p-doped and n-doped germanium. This results in an exchange of electrons and holes between the differently doped semiconducting materials. The n-doped germanium would have an excess of electrons, and the p-doped germanium would have an excess of holes. The transfer occurs until equilibrium is reached by a process called recombination, which causes the migrating electrons from the n-type to come in contact with the migrating holes from the p-type. A product of this process is charged ions, which result in an electric field.[1][2]
Excited Electrons
A difference in electric potential on a semiconducting material would cause it to leave thermal equilibrium and create a non-equilibrium situation. This introduces electrons and holes to the system, which interact via a process called ambipolar diffusion. Whenever thermal equilibrium is disturbed in a semiconducting material, the amount of holes and electrons changes. Such disruptions can occur as a result of a temperature difference or photons, which can enter the system and create electrons and holes. The process that creates and annihilates electrons and holes are called generation and recombination.[1]
Light emission
Thermal energy conversion



A large number of elements and compounds have semiconducting properties, including:[5]

  • Certain ternary compounds, oxides and alloys.
  • Organic semiconductors, made of organic compounds.


Preparation of semiconductor materials[edit]

Almost all of today’s technology involves the use of semiconductors, with the most important aspect being the integrated circuit (IC). Some examples of devices that contain integrated circuits includes laptops, scanners, cell-phones, etc. Semiconductors for IC’s are mass-produced. To create an ideal semiconducting material, chemical purity is a must. Any small imperfection can have a drastic effect on how the semiconducting material behaves due to the scale at which the materials are used.[1]

A high degree of crystalline perfection is also required, since faults in crystal structure (such as dislocations, twins, and stacking faults) interfere with the semiconducting properties of the material. Crystalline faults are a major cause of defective semiconductor devices. The larger the crystal, the more difficult it is to achieve the necessary perfection. Current mass production processes use crystal ingots between 100 and 300 mm (4 and 12 in) in diameter which are grown as cylinders and sliced into wafers.

There is a combination of processes that is used to prepare semiconducting materials for IC’s. One process is called thermal oxidation, which forms silicon dioxide on the surface of the silicon. This is used as a gate insulator and field oxide. Other processes are called photomasks and photolithography. This process is what creates the patterns on the circuity in the integrated circuit. Ultraviolet light is used along with a photoresist layer to create a chemical change that generates the patterns for the circuit.[1]

Etching is the next process that is required. The part of the silicon that was not covered by the photoresist layer from the previous step can now be etched. The main process typically used today is called plasma etching. Plasma etching usually involves an etch gas pumped in a low-pressure chamber to create plasma. A common etch gas is chlorofluorocarbon, or more commonly known Freon. A high radio-frequency voltage between the cathode and anode is what creates the plasma in the chamber. The silicon wafer is located on the cathode, which causes it to be hit by the positively charged ions that are released from the plasma. The end result is silicon that is etched anisotropically.[1][2]

The last process is called diffusion. This is the process that gives the semiconducting material its desired semiconducting properties. It is also known as doping. The process introduces an impure atom to the system, which creates the p-n junction. In order to get the impure atoms embedded in the silicon wafer, the wafer is first put in a 1100 degree Celsius chamber. The atoms are injected in and eventually diffuse with the silicon. After the process is completed and the silicon has reached room temperature, the doping process is done and the semiconducting material is ready to be used in an integrated circuit.[1][2]

Physics of semiconductors[edit]

Energy bands and electrical conduction[edit]






Charge carriers (electrons and holes)[edit]

Main article: Electron hole



Carrier generation and recombination[edit]












Early history of semiconductors[edit]










See also[edit]


  1. ^ a b c d e f g h Neamen, Donald. "Semiconductor Physics and Devices" (PDF). Elizabeth A. Jones. 
  2. ^ a b c d e Feynman, Richard (1963). Feynman Lectures on Physics. Basic Books. 
  3. ^ Shockley, William (1950). Electrons and holes in semiconductors : with applications to transistor electronics. R. E. Krieger Pub. Co. ISBN 0882753827. 
  4. ^ Brain, Marshall. "How Semiconductors Work". 
  9. ^ Louis Nashelsky, Robert L.Boylestad. Electronic Devices and Circuit Theory (9th ed.). India: Prentice-Hall of India Private Limited. pp. 7–10. ISBN 978-81-203-2967-6. 
  10. ^ a b Lidia Łukasiak and Andrzej Jakubowski (January 2010). "History of Semiconductors" (PDF). Journal of Telecommunication and Information Technology: 3. 
  11. ^ "Early history of the physics and chemistry of semiconductors-from doubts to fact in a hundred years". European Journal of Physics 10: 254–264. Bibcode:1989EJPh...10..254B. doi:10.1088/0143-0807/10/4/002. 
  12. ^

Further reading[edit]


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