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Electronic Principles
Ch. 2 - Semiconductors
27
Electrical Engineering
Undergraduate 1
01/10/2011

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Term
Ambient Temperature
Definition
Is the temperature of the surrounding air.
Term
Avalanche Effect
Definition
A phenomenon that occurs for large reverse voltages across a p-n junction. The free electrons are accelerated to such high speeds that they can dislodge valence electrons. When this happens, the valence electrons become free electrons that dislodge other valence electrons.
Term
Barrier Potential
Definition
The voltage across the depletion layer. This voltage is built into the p-n junction because it is the difference of potential between the ions on both sides of the junction. It equals approximately 0.7 V for a silicon diode.
Term
Breakdown Voltage
Definition
The maximum reverse voltage a diode can withstand before avalanche or the zener effect occurs.
Term
Conduction Band
Definition
An energy band in a semiconductor in which electrons are free to move. This energy band is one level higher than the valence band.
Term
Covalent Bond
Definition
The shared electrons between the silicon atoms in a crystal represent covalent bonds because the adjacent silicon atoms pull on the shared electrons, just as two tug-of-war teams pull o a rope.
Term
Depletion Layer
Definition
The region at the junction of p- and n-type semiconductors. Because of diffusion, free electrons and holes recombine at the junction. This creates pairs of oppositely charged ions on each side of the junction. This region is depleted of free electrons and holes.
Term
Diode
Definition
A p-n crystal. A device that conducts easily when forward-biased and poorly when reverse-biased.
Term
Doping
Definition
Adding an impurity element to an intrinsic semiconductor to change its conductivity. Pentavalent or donor impurities increase the number of free electrons, and trivalent or acceptor impurities increase the number of holes.
Term
Extrinsic Semiconductor
Definition
Refers to an doped (impure) semiconductor.
Term
Forward Bias
Definition
Applying an external voltage to overcome the barrier potential.
Term
Free Electron
Definition
One that is loosely held by an atom. Also known as a conduction-band electron because it travels in a large orbit, equivalent to a high energy level.
Term
Hole
Definition
A vacancy in the valence orbit. For instance, each atom of a silicon crystal normally has eight electrons in the valence orbit. Heat energy may dislodge one of the valence electrons, producing a hole.
Term
Intrinsic Semiconductor
Definition
Refers to a pure semiconductor. A crystal that has nothing but silicon atoms is pure or intrinsic.
Term
Junction Diode
Definition
Term
Junction Temperature
Definition
The temperature found inside a semiconductor at the p-n junction. This temperature is normally higher than the ambient temperature due to electron-hole pair recombination.
Term
Majority Carriers
Definition
Carriers are either free electrons or holes. If the free electrons outnumber the holes, the electrons are the majority carriers. If the holes outnumber the free electrons, the holes are the majority carriers.
Term
Minority Carriers
Definition
The carriers that are in the minority.
Term
n-type semiconductor
Definition
A semiconductor where there are more free electrons than holes.
Term
p-type semiconductor
Definition
A semiconductor where there are more holes than free electrons.
Term
Recombination
Definition
The merging of a free electron and a hole.
Term
Reverse Bias
Definition
Applying an external voltage across a diode to aid the barrier potential. The result is almost zero current. The only exception is when you can exceed the breakdown voltage. If the reverse voltage is large enough, it can produce breakdown through either avalanche or the zener effect.
Term
Saturation Current
Definition
The current in a reverse biased diode caused by thermally produced minority carriers.
Term
Semiconductor
Definition
A broad category of materials having four valence electrons and electrical properties between those of conductors and insulators.
Term
Silicon
Definition
The most widely used semiconductor material. It has 14 protons and 14 electrons in orbit. An isolated silicon atom has for electrons in the valence orbit. A silicon atom that is part of a crystal has eight electrons in the valence orbit because the four neighbors share one of the electrons.
Term
Surface-leakage current
Definition
A reverse current that flows along the surface of a diode. It increases when you increase the reverse voltage.
Term
Thermal Energy
Definition
Random kinetic energy possessed by semiconductor materials at a finite temperature.
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