Re: awesome

On Wed, 29 Mar 2006 15:55:04 -0600, Tim Williams wrote:


Speaking of doping, what's the difference between an LED and diode,
anyway, band gap (and Vf) aside?

The shape of the bandgap: in general bandgap is characterized by a
energy-momentum (dispersion) plot. Silicon has indirect bandgap,
i.e. the conduction band minimum is at different momentum than
the valence band maximum, so that you can't have a single photon
transition. This is because photons have energies on the order of eV but
very little momentum (practically zero). Therefore, to generate
recombination photons, we need a material where a conduction band
minimum and valence band maximum are at the wavevector.
.

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