Carrier Actions

What Actions?
Definitions
Drift Current
Diffusion Current
Mobility & Scattering
What causes band bending?
Recombination
Generation
Let's Draw!
Related Topics

Generation

Generation can be taken as the opposite of recombination. The generation of carriers is another part of the process to restore equilibrium to a semiconductor that has been perturbed, or disturbed out of equilibrium. Perturbations can be in the form of an applied electric field, a change in temperature or exposure to light. Generation occurs when there's a deficit in carrier concentration, when compared to equilibrium carrier concentration. Carriers then have to be created within the semiconductor to reach equilibrium.

The three mechanisms of recombination can be reversed to create carriers. The three ways are band-to-band generation, R-G center generation, and Auger generation. Band-to-band generation can occur when an electron is exited directly into the conduction band. This can occur by obsorbing thermal energy or light. When generation occurs by absorbing thermal energy, this is called direct thermal generation and when externally applied light is absorbed, it is called photogeneration. R-G centers can also be used for generation. The electron would not need as much energy to make it to the conduction band as it would need for band-to-band generation. Auger generation occurs just as in recombination. This occurs more often when an electric field is applied, though.

To see recombination and generation occurring, using all three mechanisms, take a look at the demo. It shows, band-to-band generation-recombination by clicking on "Surface" or "Radiative". To see recombination-generation using R-G centers, click on "Thermal R-G".

In order to run the demo, you need Shockwave installed for your browser. The Vectras should run it properly, but the Sun workstations will not. Also, for better viewing, use the "full screen" option on your browser. After you're done viewing, use the browser's "back" button to return to this page.


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