An analysis was done on the type of doping elements which can be added with Silicon material. Pure Silicon has four electrons in valence band. If pure Silicon is doped with bivalent element like Calcium as acceptor impurity, this provides two free protons in the conduction band of the Si Crystal and this can be used as p-type material for the photo diode. If pure Silicon is doped with hexavalent element like Sulfur as donor impurity, this forms two electron in the conduction band of the Si Crystal and this can be used as n-type material for the photo diode. By this method, the number of pairs of free electron and free proton can be increased in the photo diode.
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