5M10.18 Gallium Arsenide Corona Discharge
Semiconductor bands, corona discharge, dielectrics, photodoping
A sharp conductor on the Van de Graaff generator will emit electrons via corona discharge and prevent arcing to an adjacent grounded tower. A shard of GaAs on a Van de Graaff generator will also undergo corona discharge if photodoped with room lights or a flashlight. In total darkness, the GaAs does not conduct, so the Van de Graaff arcs to the grounded tower.
-  Van de Graaff generator
-  Grounding tower
-  Discharge wand
-  Mounted GaAs shard
-  Thumbtack
-  Flashlight
-  Extension cord
- Put the Van de Graaff somewhere away from computers and plug it in.
- Place the grounding tower within arcing distance of the Van de Graaff.
- Ensure the Van de Graaff is not near any computers or other electronics.
- Users should not be have their phones or other electronics.
- Turn off the lights.
- Perform the dielectric breakdown experiment, leaving the grounded tower close enough to spark.
- Tape the pin on top of the Van de Graaff dome, pointy end up.
- Start the Van de Graaff. No sparks should occur due to the corona discharge off the pin.
- Ground the Van de Graaff and turn it off.
- Replace the pin with a piece of semiconductor.
- Turn off all the lights.
- Turn on the Van de Graaff. Sparks should fly from the Van de Graaff to the grounding tower.
- Shine the flashlight at the semiconductor. Sparks should stop.
- Turn off the flashlight, ground the Van de Graaff, and turn off the generator.
- PIRA 5M10.18
- Don't attempt this at home!
- Lattice models
- Van de Graaff generator
If you have any questions about the demos or notes you would like to add to this page, contact Ricky Chu at ricky_chu AT sfu DOT ca.