ECE 231 -12

ECE 231 -12 - ECE-231 Circuits and Systems I Fall 2011...

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ECE-231 Circuits and Systems I Fall 2011 Session 12 Dr. Stewart Personick Office: ECEC Room 331 [email protected]
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Semiconductor-based Electronic Devices: Diodes and Transistors
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Semiconductors Conceptual 2-dimensional representation of crystalline Silicon (Si). Each Si atom has 4 electrons in its outer shell. Each Si atom “shares” 1 of these 4 electrons with its 4 nearest neighbors (covalent bond) .
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Semiconductors + At any temperature above absolute zero, there will be some electrons that gain enough thermal energy to break its covalent bond, and to roam freely within the silicon crystal. This results in a negatively charged “free” electron, and a positively charged silicon ion (“hole”). e
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Semiconductors + At any temperature above absolute zero, there will be some electrons that gain enough thermal energy to break its covalent bond, and to roam freely within the silicon crystal. This results in a negatively charged “free” electron, and a positively charged silicon ion (“hole”). If an electron from a silicon atom that is (for example ) to the right of the hole (i.e. to the right the silicon atom with the missing electron) jumps to the left… to “fill the hole”… then this results in the hole moving to the right e
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Semiconductors + e At any temperature above absolute zero, there will be some electrons that gain enough thermal energy to break its covalent bond, and to roam freely within the silicon crystal. This results in a negatively charged “free” electron, and a positively charged silicon ion (“hole”). If an electron from a silicon atom that is (for example ) to the right of the hole (i.e. to the right the silicon atom with the missing electron) jumps to the left… to “fill the hole”… then this results in the hole moving to the right However , in a pure silicon crystal, it is much “easier” for free electrons to move around than it is for holes to move around… for example, in the presence of an electric field
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Semiconductors If one substitutes an atom that has 5 electrons in its outer shell for a silicon atom… then (at temperatures well above absolute zero, e.g. room temperature) it is highly probable that the extra electron associated with that atom will break free and roam freely within the crystal. Examples of such “donor” atoms are: nitrogen (N), phosphorus (P) and arsenic (As). It is much easier for these donated electrons to move around within the crystal than it
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This note was uploaded on 03/01/2012 for the course ECE 231 taught by Professor Pietrucha during the Spring '08 term at NJIT.

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ECE 231 -12 - ECE-231 Circuits and Systems I Fall 2011...

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