The Doping of Semiconductors

The Doping of Semiconductors - Index Semiconductor concepts...

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The Doping of Semiconductors The addition of a small percentage of foreign atoms in the regular crystal lattice of silicon or germanium produces dramatic changes in their electrical properties, producing n-type and p-type semiconductors. Pentavalent impurities Impurity atoms with 5 valence electrons produce n-type semiconductors by contributing extra electrons. Trivalent impurities Impurity atoms with 3 valence electrons produce p-type semiconductors by producing a " hole " or electron deficiency. Index Semiconductor concepts P- and N- Type Semiconductors Index Semiconductor concepts
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N-Type Semiconductor The addition of pentavalent impurities such as antimony, arsenic or phosphorous contributes free electrons, greatly increasing the conductivity of the intrinsic semiconductor . Phosphorous may be added by diffusion of phosphine gas (PH3).
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Unformatted text preview: Index Semiconductor concepts P-Type Semiconductor The addition of trivalent impurities such as boron, aluminum or gallium to an intrinsic semiconductor creates deficiencies of valence electrons,called "holes". It is typical to use B 2 H 6 diborane gas to diffuse boron into the silicon material. Index Semiconductor concepts Bands for Doped Semiconductors The application of band theory to n-type and p-type semiconductors shows that extra levels have been added by the impurities. In n-type material there are electron energy levels near the top of the band gap so that they can be easily excited into the conduction band. In p-type material, extra holes in the band gap allow excitation of valence band electrons, leaving mobile holes in the valence band. Index Semiconductor concepts...
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The Doping of Semiconductors - Index Semiconductor concepts...

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