Semiconductors Definition and 25 Discussions

A semiconductor material has an electrical conductivity value falling between that of a conductor, such as metallic copper, and an insulator, such as glass. Its resistivity falls as its temperature rises; metals behave in the opposite way. Its conducting properties may be altered in useful ways by introducing impurities ("doping") into the crystal structure. When two differently-doped regions exist in the same crystal, a semiconductor junction is created. The behavior of charge carriers, which include electrons, ions and electron holes, at these junctions is the basis of diodes, transistors and most modern electronics. Some examples of semiconductors are silicon, germanium, gallium arsenide, and elements near the so-called "metalloid staircase" on the periodic table. After silicon, gallium arsenide is the second most common semiconductor and is used in laser diodes, solar cells, microwave-frequency integrated circuits, and others. Silicon is a critical element for fabricating most electronic circuits.
Semiconductor devices can display a range of useful properties, such as passing current more easily in one direction than the other, showing variable resistance, and sensitivity to light or heat. Because the electrical properties of a semiconductor material can be modified by doping, or by the application of electrical fields or light, devices made from semiconductors can be used for amplification, switching, and energy conversion.
The conductivity of silicon is increased by adding a small amount (of the order of 1 in 108) of pentavalent (antimony, phosphorus, or arsenic) or trivalent (boron, gallium, indium) atoms. This process is known as doping and the resulting semiconductors are known as doped or extrinsic semiconductors. Apart from doping, the conductivity of a semiconductor can be improved by increasing its temperature. This is contrary to the behavior of a metal in which conductivity decreases with an increase in temperature.
The modern understanding of the properties of a semiconductor relies on quantum physics to explain the movement of charge carriers in a crystal lattice. Doping greatly increases the number of charge carriers within the crystal. When a doped semiconductor contains free holes it is called "p-type", and when it contains free electrons it is known as "n-type". The semiconductor materials used in electronic devices are doped under precise conditions to control the concentration and regions of p- and n-type dopants. A single semiconductor device crystal can have many p- and n-type regions; the p–n junctions between these regions are responsible for the useful electronic behavior. Using a hot-point probe, one can determine quickly whether a semiconductor sample is p- or n-type.Some of the properties of semiconductor materials were observed throughout the mid 19th and first decades of the 20th century. The first practical application of semiconductors in electronics was the 1904 development of the cat's-whisker detector, a primitive semiconductor diode used in early radio receivers. Developments in quantum physics led in turn to the invention of the transistor in 1947, the integrated circuit in 1958, and the MOSFET (metal–oxide–semiconductor field-effect transistor) in 1959.

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  1. F

    B Field distribution in semiconductors

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  2. A

    Silicon and Germanium semiconductor mixtures used in component manufacturing?

    Can Silicon and Germanium semiconductors mixture (chemical reaction) with some other chemical elements (if required) assist in creating new and existing robust electronic components? Si + Ge + ? + ? = Can this assist in quantum computing?
  3. Praveen1901

    B P-N junction Semiconductors

    I'm new to semiconductors. While I was studying types of biasing in semiconductors, here's what I read - 'In forward biasing, the width of the depletion region is reduced.' Here's what I thought - Since the potential barrier is reduced in the junction due to external potential, the diffusion...
  4. Joaco

    Studying Condensed Matter Physics Grade vs Materials Science?

    Hi, I'm an undergrad materials engineering student. I am thinking of studying all the way to a PhD as I'm interested on working in research. Right now I work with Semiconductors and I like the field a lot. However, considering what I'm studying, I want to know if it's a good Idea to look for a...
  5. B

    A Interface states in a PIN diode

    Is the equation used to determine the density of interface states in schottky diodes from capacitance- frequency data applicable to PIN junctions?
  6. M

    Metal thin film adhesion, Au-Si deposition

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  7. A

    I Fluorescence from core shell quantum dots

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  8. A

    I Semiconductor doping

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  9. M

    Impact of crystal defects on band diagram.?

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  10. H

    Increase the maximum voltage rating of semiconducter

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  11. E

    I Number of electrons in conduction band

    Hello! In order to obtain the number of actual electrons in the conduction band or in a range of energies, two functions are needed: 1) the density of states for electrons in conduction band, that is the function g_c(E); 2) the Fermi probability distribution f(E) for the material at its...
  12. E

    I Double heterostructure junction in forward and zero bias

    Hi! When dealing with a pn homojunction, it is easy to see the features it has at equilibrium, and also the features it has with forward/reverse bias. Plots show the constant Fermi level at equilibrium and the different Fermi levels for a forward bias; moreover, examples show how much the bands...
  13. E

    I Built-in potential in pn junction

    Hello! The (potential) energy of an electron in a solid structure is always negative; also the E_c and E_v levels (conduction band and valence band limits) are negative, in the band diagram of a pn junction. When the junction is built and thermal equilibrium is reached, the depletion region...
  14. Y

    I How to get plot (optical gain of GaAs)?

    How can i calculate this plot (photon energy dependence of the optical gain (or loss = negative gain) of GaAs with the injected carrier density as a parameter? Show calculated plot based on this equation Given parameter: mc=0.067 me; (effective mass of electrons in conduction band) mv=0.48...
  15. E

    I Pn junction to reach thermal equilibrium

    Hello! Some of the processes caused by a pn junction are not clear for me. Just after the contact between the p and the n region, a migration of charges happens in a semiconductor junction in order to reach an equilibrium condition. A valence band and a conduction band are present in both...
  16. R

    I Velocity saturation and mobility in metals and semiconductor

    Hi, Lately, I've been trying to compare and understand conduction properties of metals and semiconductors. However, there are two question on my mind that I'm still trying to figure out. Maybe someone here might be able to provide some clues. 1. It is known that a linear increase of the...
  17. Jess H. Brewer

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    Hi, I'm a retired (since 2011) Physics prof from the University of British Columbia. I originally set out to get a PhD in Physics to increase my credibility as a science fiction writer, but I discovered a field* that was so cool it was like being a character in my own SF novel. In short, I got...
  18. Benevito

    Photoluminescence at a heterojunction

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  19. U

    2D problem of nearly free electron model

    Homework Statement (a) Find energies of states at ##(\frac{\pi}{a},0)##. (b) Find secular equation Homework Equations The Attempt at a Solution Part(a)[/B] In 1D, the secular equation for energy is: E = \epsilon_0 \pm \left| V(x,y) \right| When represented in complex notation, the...
  20. L

    What is the biggest challenge to improve white LEDs?

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  21. H

    What does the wavevector "k" mean in the Schrödinger eq. ?

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  22. thegreengineer

    Basic Electronics: Transistor confusion

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  23. C

    Free electron concentration range between semiconductors and metals

    A structure with free electron density around 10^26 m^-3 is considered as a highly doped semiconductor or a metal? Or in other words, what is the lowest possible free electron concentration for a metal and what is the highest possible free electron concentration for a doped semiconductor?
  24. G

    Calculating electron and hole population in a semiconductor

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  25. Christian0412

    Calculating Bandgaps Experimentally

    I've been doing a bit of reading on bandgaps of semiconductors and alloys of semiconductors. I was curious to know is the bandgap of a material, say Silicon, determined or calculated experimentally? How do scientists usually determine this in the lab?