Electronics-I Lecture 12

Electronics-I Lecture 12 - BasicSemiconductorConcepts

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Lecture 12 Electronics I 1 Basic Semiconductor Concepts Thermal Ionization results in Free electrons Free holes Equal number Move randomly through silicon crystal Recombination Free electrons and holes combine Recombination rate proportional to number of free  electrons and holes which is proportional to ionization  rate
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Lecture 12 Electronics I 2 Basic Semiconductor concepts Ionization rate is a strong function of  temperature In thermal equilibrium, recombination rate  is equal to ionization  n = p = n i  (concentration of holes or  electrons in intrinsic silicon/cm 3 ) kT / E 3 2 i G e BT n - =
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Lecture 12 Electronics I 3 Basic Semiconductor concepts B material dependant parameter = 5.4 x 10 31  for Silicon E G  bandgap energy = 1.12 eV for Silicon k Boltzmann’s constant = 8.62 x 10 -5  eV/K At room temperature (T = 300 K)  n i = 1.5 x 10 10  carriers/cm 3 Silicon crystal has 5 x 10 22  atoms/cm 3   At room temperature only one of every billion atom is  ionized kT / E 3 2 i G e BT n - =
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Lecture 12 Electronics I 4 Basic Semiconductor concepts Diffusion and Drift Two mechanisms by which electrons/hole move through a silicon  crystal Diffusion Random motion due to thermal agitation cause uniform  concentration of holes and free electrons
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This note was uploaded on 12/12/2010 for the course EE 1 taught by Professor Shahidanwar during the Spring '10 term at NUCES.

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Electronics-I Lecture 12 - BasicSemiconductorConcepts

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