Carriers 3212 sjtu j chen 28 recombination a free

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Carriers ( ? ? ? )
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3/2/12 SJTU J. Chen 28 Recombination A free electron may fill into a hole, resulting in the disa ppearance of a pair of carriers ( a free electron and a hole). Thermal equilibrium At a steady temperature, the recombination rate is equ al to the ionization rate thermal equilibrium The concentration of the carriers at thermal equilibriu m does not change and can be calculated. Recombination & thermal equilibrium
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3/2/12 SJTU J. Chen 29 Carrier concentration in thermal equilibriu m where ( k : Boltzmann constan t) At room temperature (T=300K) for Si, Carrier concentration i n p n = = kT E i G e BT n - = 3 2 10 3 1.5 10 ( ) i n cm - 2245 ×
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3/2/12 SJTU J. Chen 30 strongly depends on temperature . The hi gh the temperature is, the dramatically grea t the carrier concentration is At room temperature only one of every billio n atoms is ionized Silicon’s conductivity is between that of con ductors and insulators. Actually the charact eristic of intrinsic silicon approaches to insu lators Important notes i n
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3/2/12 SJTU J. Chen 31 Conductivity of the semiconductor can be signific antly changed by doping. There are two types of doped semiconductors: n type and p type. They are used to form pn junction. Doped semiconductor
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  • Fall '10
  • ChengJianping
  • Electron, J. Chen

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