Semiconductors

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© 1998-2008 by Glenn Elert -- A Work in Progress
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Discussion

Just ask Brittney Spears, a semiconductor is a material whose electrical conductivity is between that of a conductor and an insulator. The elements most commonly used in semiconducting devices are silicon and germanium.

donors, acceptors / electrons, holes

model	donor (charge carrier)	acceptor
electron	negative	positive
hole	positive	negative

Semiconductors

1. Bipolar Metal Oxide Semiconductor (BMOS)
   description
2. Positive-Channel Metal Oxide Semiconductor (PMOS)
   description
3. Negative-Channel Metal-Oxide Semiconductor (NMOS)
   description
4. Complementary Metal Oxide Semiconductor (CMOS)
   A semiconductor fabrication technology using a combination of n- and p-doped semiconductor material to achieve low power dissipation. Any path through a gate through which current can flow includes both n and p type transistors. Only one type is turned on in any stable state so there is no static power dissipation and current only flows when a gate switches in order to charge the parasitic capacitance.
   1. N-Channel CMOS (NCMOS)
      Silicon Gate Reversed
   2. eXtended CMOS (XCMOS)
      description
   3. BiCMOS
      A manufacturing process for semiconductor devices that combines bipolar and CMOS to give the best balance between available output current and power consumption.

Semiconductor Devices

Diodes

A semiconductor device which conducts electric current run in one direction only. This is the simplest kind of semiconductor device, it has two terminals and a single PN junction. One diode can be used as a half-wave rectifier or four as a full-wave rectifier.

Transistors

Because they "transfer resistance", like "resistors" they are"transistors".

A three terminal semiconductor amplifying device, the fundamental component of most active electronic circuits, including digital electronics.

1. point contact transistor
   "Proof of Principle" device. A dead end. The transistor was invented on 1947-12-23 at Bell Labs.
2. bipolar transistor (a.k.a. junction transistor, sandwich transistor)
   A transistor made from a sandwich of n- and p-type semiconductor material: either npn or pnp. The middle section is known as the "base" and the other two as the "collector" and "emitter". When used as an amplifying element, the base to emitter junction is in a "forward-biased" (conducting) condition, and the base to collector junction is "reverse-biased" or non-conducting. Small changes in the base to emitter current (the input signal) cause either holes (for pnp devices) or free electrons (for npn) to enter the base from the emitter. The attracting voltage of the collector causes the majority of these charges to cross into and be collected by the collector, resulting in amplification.
3. field effect transistor (FET)
   A transistor with a region of donor material with two terminals called the "source" and the "drain", and an adjoining region of acceptor material between, called the "gate". The voltage between the gate and the substrate controls the current flow between source and drain by depleting the donor region of its charge carriers to greater or lesser extent. Because no current (except a minute leakage current) flows through the gate, FETs can be used to make circuits with very low power consumption.
   1. Junction Field Effect Transistor (JFET)
      A Field Effect Transistor in which the conducting channel lies between pn junctions in the silicon material. A pn junction acts as a diode, so it becomes conductive if the gate voltage gets reversed.
   2. Metal Oxide Semiconductor Field Effect Transistor (MOSFET)
      Most of today's transistors are MOSFETs.

Summary

• bullet

Problems

practice

1. Write something.
   • Answer it.
2. Write something.
   • Answer it.
3. Write something.
   • Answer it.
4. Write something completely different.
   • Answer it.

numerical

1. problems

Resources

• general
  • Britney Spears guide to Semiconductor Physics (by the pint-sized queen of pop herself)

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