The Main feature of intrinsic S-conductor are ;
- R More pure than metal conductors and less than insulator
- With negative temperature coefficient as R decrease with the rise in temperature .
- Valence electron is plus minus 4.This values means that atom has four electrons in the outermost ring-half to the goal of 5 .
By adding impurities the conductivity of material can increase which is the special feature of semi-conductor .This process of adding impurity element is called doping .The purpose is to increase the number of free charges that can be move by an external applied voltage .When the Number of free electrons is increased ,the doped semi-conductor is negative or N-type: Reducing number of free electron makes material P-types.Genrmanium (Ge) and Silicon can be used with either P-type or N-Type doping but silicon S-conductor devices are most common.
Semi –Conductor and Doping Elements.
|Element||Symbol||Atomic Number||No of Valence electrons|
|Acceptor impurities elements Take electrons to form P-type S-Conductor ,Ga and In used for Ge ,Al and B for Si|
|Intrinsic S-conductor Used in pure crystal form to be doped with impurities elements.Doped S-conductor are extrinsic|
|Donor impurities elements Give electrons to form N-type S-conductor ,As and Sb used for Ge and Phosphorous for Si.|
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