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| 1. |
Explain why does conductivity of germanium crystals increase on doping with gallium . |
| Answer» Solution :Germanium (GE) belongs to Group 14 while Gallium (GA) belongs to Group 13. Ge has 4 ELECTRONS in the valence shell whereas Ga has only 3. When Ge is replaced by Ga, an electron vacancy is created Electrons from neighbouring atoms move to FILL this vacancy . As a result, a hole is created in its original position. When an electric FIELD is applied , electrons move towards the position plate and conduct electricity. The holes move towards the negative plate. | |