P-N Junction Essay

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p-n DIODE OR p-n JUNCTION: “A p-n diode or p-n junction is a two terminal device formed by joining a p-type and n-type semi-conductors.” A junction between p-type and n-type is formed where holes and electrons diffuse into each other thereby forming a depletion layer. The thickness of depletion layer provides a potential barrier which prevent further migration of holes and electrons through depletion layer. Thickness of depletion layer could be increased or decreased by varying the potential of the potential barrier, which increases or decreases the conductivity of diode. A p-n diode could be used in electrical circuits across a battery, as it permits the flow of current in one direction only. By themselves, P-type (positively charged) and N-type (negatively charged) semiconductors are just conductors. But if you put them together on an electronic circuit, you create a p-n junction and an interesting and very useful thing happens: Current can flow through the p-n junction, but only in one direction. If you put positive voltage on the p side of the junction and negative voltage on the n side, current flows through the junction. But if you reverse the voltage, putting negative voltage on the p side and positive voltage on the n side, current doesn't flow. P-TYPE SEMI-CONDUCTOR: The addition of trivalent impurities such as boron, aluminum or gallium to an intrinsic semiconductor i.e. pure Si or Ge creates deficiencies of valence electrons, called "holes". N-TYPE SEMI-CONDUCTOR: The addition of pentavalent impurities such as antimony, arsenic or phosphorous contributes free electrons, greatly increasing the conductivity of the intrinsic semiconductor i.e. pure Si or Ge. In n-type substances charge carriers are the electrons. OPERATION OF A FORWARD BIASED p-n JUNCTION: “When external voltage is applied to the p-n junction in such a direction that it cancels the

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