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- PHY102 Physics II © Dr.Cem Özdoğan
- A semiconductor is like an insulator except that the energy required to free some electrons is not quite so great.
- In a semiconductor, n is small but increases very rapidly with temperature as the increased thermal agitation makes more charge carriers available.
- This causes a decrease of resistivity with increasing temperature.
- The resistivity in a conductor is given by:
- Pure silicon has a high resistivity and it is effectively an insulator. However, its resistivity can be greatly reduced in a controlled way by adding minute amounts of specific “impurity” atoms in a process called doping.
- The process of doping can supply electrons or positive charge carriers that are very loosely held within the material and thus are easy to get moving.
- Also, by controlling the doping of a semiconductor, one can control the density of charge carriers that are responsible for a current.