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Silicon Bandgap Energy


narrowbandpaul

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The silicon bandgap energy is the energy needed to promote an electron to the conduction band. In the conduction band, the electron is free to move under external forces and be collected in electric fields.

This is what happens when your SLR's and CCD's recieve light. The photon supplies the energy to the electron, and the electric fields store the charge.

The attached pdf shows how the bandgap changes as we change temperature.....

a lower energy means a slightly better infrared response, but we need to warm the sensor= LOTS OF DARK CURRENT

cooling the sensor help alleviate dark current, but at the expense of a slightly poorer NIR response.

Thanks for looking

Paul

Silicon Bandgap Energy dependence on Temperature.pdf

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Check out Black Silicon....that will give you bags and bags of IR response...and bags more visible response as well. Not sure what the noise will be like, but with such a high responsivity, the S/N should be better than standard silicon. This stuff should be replacing normal silicon in cameras within a couple of years.

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If only the astro club didnt have to rely on sensors designed for things other than astro that happen to be useful, rather had our own affordable astro designed sensors. one day perhaps.

Speaking of which, has everybody seen the new Planck findings?

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Thanks Paul.

I like to know how this stuff works...it all helps, and an uderstanding of the process is neccessary I think.

Re. Black silicon....intriguing...tell us more ;)

Cheers

Rob

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Given that the article says it absorbs light out to 2 microns (really not sure *how* it does that), you'd better have a nice liquid nitrogen cooling system for your instrument detector as well, if you don't want to swamped with thermal background... ;)

Silicon CCDs have quantum efficiencies up to 95% in the visible -- they're already collecting almost all the photons available...

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