N-Type Silicon
• Pentavalent impurities such as phosphorus, arsenic, antimony, and bismuth have 5 valence electrons.
• When phosphorus impurity is added to Si, every phosphorus atom’s four valence electrons are locked up in covalent bond with valence electrons of four neighboring Si atoms. However, the 5th valence electron of phosphorus atom does not find a binding electron and thus remains free to float. When a voltage is applied across the silicon-phosphorus mixture, free electrons migrate toward the positive voltage end.
• When phosphorus is added to Si to yield the above effect, we say that Si is doped with phosphorus. The resulting mixture is called N-type silicon (N: negative charge carrier silicon).
• The pentavalent impurities are referred to as donor impurities.
P-Type Silicon
• Trivalent impurities e.g., boron, aluminum, indium, and gallium have 3 valence
electrons.
• When boron is added to Si, every boron atom’s three valence electrons are locked up in covalent bond with valence electrons of three neighboring Si atoms. However, a vacant spot “hole” is created within the covalent bond between one boron atom and a neighboring Si atom. The holes are considered to be positive charge carriers.
When a voltage is applied across the silicon-boron mixture, a hole moves toward the negative voltage end while a neighboring electron fills in its place.
• When boron is added to Si to yield the above effect, we say that Si is doped with boron. The resulting mixture is called P-type silicon (P: positive charge carrier silicon).
• The trivalent impurities are referred to as acceptor impurities
• The hole of boron atom points towards the negative terminal.
• The electron of neighboring silicon atom points toward
positive terminal.
• The electron from neighboring silicon atom falls into the boron atom filling the hole in boron atom and creating a “new” hole in the silicon atom.
• It appears as though a hole moves toward the negative terminal!
• Pentavalent impurities such as phosphorus, arsenic, antimony, and bismuth have 5 valence electrons.
• When phosphorus impurity is added to Si, every phosphorus atom’s four valence electrons are locked up in covalent bond with valence electrons of four neighboring Si atoms. However, the 5th valence electron of phosphorus atom does not find a binding electron and thus remains free to float. When a voltage is applied across the silicon-phosphorus mixture, free electrons migrate toward the positive voltage end.
• When phosphorus is added to Si to yield the above effect, we say that Si is doped with phosphorus. The resulting mixture is called N-type silicon (N: negative charge carrier silicon).
• The pentavalent impurities are referred to as donor impurities.
P-Type Silicon
• Trivalent impurities e.g., boron, aluminum, indium, and gallium have 3 valence
electrons.
• When boron is added to Si, every boron atom’s three valence electrons are locked up in covalent bond with valence electrons of three neighboring Si atoms. However, a vacant spot “hole” is created within the covalent bond between one boron atom and a neighboring Si atom. The holes are considered to be positive charge carriers.
When a voltage is applied across the silicon-boron mixture, a hole moves toward the negative voltage end while a neighboring electron fills in its place.
• When boron is added to Si to yield the above effect, we say that Si is doped with boron. The resulting mixture is called P-type silicon (P: positive charge carrier silicon).
• The trivalent impurities are referred to as acceptor impurities
• The hole of boron atom points towards the negative terminal.
• The electron of neighboring silicon atom points toward
positive terminal.
• The electron from neighboring silicon atom falls into the boron atom filling the hole in boron atom and creating a “new” hole in the silicon atom.
• It appears as though a hole moves toward the negative terminal!
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