Dear all, I came to know that the conductivity modulation is process of doping to increase conductivity of semiconductor. But can anyone suggest various steps/process involved in this?
hello...
i suggest you to look up the wikipedia article on semiconductor doping. it gives a nice overview on the techniques and steps you need to know.
http://en.wikipedia.org/wiki/Doping_%28semiconductor%29
The conductivity modulation can be performed by technological process - doping - thermal processes, diffusion, implantation, or by electrical stimulus.
For instance, when the gate of a MOS is biased, under the oxide, the conductivity is modulated by the gate voltage magnitude. A depletion zone means lower carrier concentration - equivalent with a conductivity decreasing - this is the conductivity modulation induced by field.
Let's take the example of a power diode..when forward biased, by double injection, the drift area gets large amounts of electrons and holes, larger than the population already there (however the drift area in a power device is low doped) and that means bigger carrier concentration and increasing conductivity..
Excess p and n type carriers defuse and recombine inside the drift region. If the width of the drift region is less than the diffusion length of carries then the spatial distribution of excess carrier density in the drift region will be fairly flat and several orders of magnitude higher than the thermal equilibrium carrier density of this region. Conductivity of the drift region will be greatly enhanced as a consequence (also called conductivity modulation).
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