11.SSD (EE-2080)_Lecture11 [Compatibility Mode]

11.SSD (EE-2080)_Lecture11 [Compatibility Mode] - SDM(EE...

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DM(EE- 080) SDM(EE 2080) Lecture 11 Dr. Shiv Govind Singh sgsingh@iith.ac.in gg @ Assistant Professor Electrical Engineering Semester 2, Y-2010/11
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Reference Text Book: hysics of Semiconductor Devices MS ze John Wiley & Sons (1981) 1. Physics of Semiconductor Devices, S. M. Sze , John Wiley & Sons (1981). 2. Solid State Electronics by Ben G. Streetman and Sanjay Banerjee , Prentice Hall International , Inc. Semiconductor Physics and Devices Donald A Neamen Tata 3. Semiconductor Physics and Devices, Donald A. Neamen, Tata Mcgraw-Hill Publishing company Limited. Reference Book: 1 . Fundamentals of Solid-State Electronic Devices, C. T. Sah , Allied Publisher and World Scientific, 1991. 2. Complete Guide to Semiconductor Devices, K. K. Ng , McGraw Hill, 1995. 3. Solid state physics, Ashcroft & Mermins . 4. Introduction to Solid State Electronics, E. F. Y. Waug , North Holland, 1980.
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ecap Recap ensity of States Density of States • Fermi level • Conclusion
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Outline lectron and holes in semiconductor Electron and holes in semiconductor • More details about semicondutor
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p Electron in semiconductor = top c E E o dE E g E f n ) ( ) ( = top E c n dE E E m n ( 3 2 / 3 * h May not be integrable + c E F o kT E E / ) exp( 1 Apply MB distribution as Eg/2~16KT ) ( 3 2 / 3 * ( E E c n f c dE E E m / ) exp( kT c E F o e N kT E E n = = h 9 * 19 2 / 3 2 10 ) ( 2 = h π kT m N n c Effective density of states in CB
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Filled no of states gives the no. of electrons g For heavily doped the semiconductor MB distribution does not hold so, need to solve Fermi integral for solution. e.g let us take n=10 20 e get E E hich is not possible We get E F >E c which is not possible E E N ( 2 So = kT F n C c 2 / 1 0 π
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oles in semiconductor Holes in semiconductor = Ev dE E g E f p ) ( )} ( 1 {( E v o bott p E m 2 / 3 * kT E E v E F v o v F e N kT E E dE E E p ) ( 3 / ) exp( ( = = h 2 / 3 * ) ( 2 kT m N v = 2 h π v p n m m * * Since v c N N
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Fermi level in intrinsic semiconductor at equilibrium m m * * v c p n N N dos dos But at Equilibrium n 0 =p 0 ) ( ) ( v F F c E E E E * dos p V C kT v kT m E E N Nc + = * * * , ln 2 os os dos n p n F m m if m kT E = + dos dos E F will be in middle of band gap
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Equilibrium Distribution of Electrons and Holes Intrinsic semiconductor in Intrinsic semiconductor E ) f ) E g c (E) g c (E) g c (E). f f (E) f f (E) E c Area n 0 = electrons concentration E c E F E V Area p 0 = holes concentration E g v (E) g v (E) g c (E). (1-f f (E)) E V f f (E)=0 f f (E)=1
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Intrinsic carrier concentration Product of n 0 and p 0 kT E E v F ) ( = N c (/cm 3 ) (10 18 ) N v (/cm 3 ) (10 18 ) * n m * p m v o e N p kT E E F c ) ( = Si 28 10.4 1.08 .56 e o m o m c o e N n kT E E c kT E E v o o F c v F e N e N p n = ) ( ) ( Ge 10.9 6 .55 .37 GaAs .47 7 .067 .48 kT E c v kT E E c v o o g v c e N N e N N p n = = ) ( E g (eV) Concentrat ion (/cm 3 ) 300K Concentrati on (/cm 3 ) 400K Where E is band gap, o o kT E c v i p n e N N n g = = 2 Si 1.12 1.510 10 ~10 13 Ge .72 2.4X10 13 ~10 16 g gp , At equilibrium n o =p o =n i n i depends upon temperature and band gap GaAs 1.42 1.8X10
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This note was uploaded on 07/19/2011 for the course EE 211 taught by Professor Sgsingh during the Spring '11 term at IIT Kanpur.

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11.SSD (EE-2080)_Lecture11 [Compatibility Mode] - SDM(EE...

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