|MadSci Network: Chemistry|
Hi Bilal Bhatti, Negative and positive charge ALWAYS attract each other, NEVER repel. This is the same in a semiconductor as any- where else. Maybe I don't understand your question. I will try to explain what happens in a semiconductor and hope that clarifies the misunderstanding. Please feel free to contact me or other Mad Scientists again if it doesn't. In a non-doped semiconductor, there are exactly as many electrons as needed to hold the inter-atomic bonds. Electrons in bonds cannot move and therefore do not conduct current. A non-doped semiconductor is thus an insulator. If we, by doping, introduce excess electrons or missing ones (=holes, which carry a positive charge), those can move around and carry current. If an excess electron meets a hole, they annihilate and emit their energy as light or heat. At a p-n-junction, all excess electrons and holes near the junction are attracted to each other and annihilate, thus creating a zone with no free carriers. Hope this helps. Greetings from Singapore, Frank Berauer
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