PCS 224 Lecture Notes - Lecture 5: Drift Current, Drift Velocity, Covalent Bond
27 Nov 2015
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Document Summary
When an electron breaks apart the covalent bond, it creates a hole. Doping (extrinsic) impure by adding small impurity atoms. An impurity such as phosphrous would be in a different group and causes there to be a free electron. A crystal of silicon has 1 atom out of every 10^8 atoms replaced with an. N si = 5 x 10^22 cm ^-3. Nd = nsi / 10^8 = 5 x 10 ^14 cm ^-3. An impurity in group 3 is called an acceptor (na). The whole concentration decreases and that is why po is smaller. Majority concentration = | na nd| if you have more acceptor than it would be ptype. Or more donor than n type (table 1. 3) In p type you have fixed negative charges, the positive charges are free to move around. In n type you have fixed positive charges where the negative charges move around.
