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01_exam1fall - Page 1 of 8 YOUR NAME_ Department of...

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Page 1 of 8 YOUR NAME________________________________ Department of Electrical Engineering and Computer Science Massachusetts Institute of Technology 6.012 Electronic Devices and Circuits Exam No. 1 Notes: 1. Unless otherwise indicated, assume room temperature and that kT/q is 0.025 V. You may also approximate [(kT/q) ln 10] as 0.06 V. 2. Open book: 6.012 text and one sheet of notes permitted. 3. All of your answers and any relevant work must appear on these pages. Any additional paper you hand in will not be graded. 4. Make reasonable approximations and assumptions. State and justify any such assumptions and approximations you do make. 5. Be careful to include the correct units with your answers when appropriate. 6. Be certain that you have all eight (8) pages of this exam booklet and make certain that you write your name at the top of this page in the space provided. 6.012 Staff Use Only PROBLEM 1 (out of a possible 33) PROBLEM 2 (out of a possible 33) PROBLEM 3 (out of a possible 34) TOTAL
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Your name Page 2 of 8 Problem 1 - (33 points) This question concerns several silicon samples. In these samples the electron mobility, µ e , is 1600 cm 2 /V-s; the hole mobility, µ h , is 600 cm 2 /V-s; the minority carrier -3 lifetime, t min , is 10 -5 s; and the intrinsic carrier concentration, n i , is 10 10 cm at room temperature. Except in Part e, there are no contacts on these samples and all of their surfaces are reflecting boundaries, i.e. there is no extra recombination there. a) One sample is doped with 1 x 10 16 cm -3 boron atoms and 2 x 10 16 cm -3 phosphorous atoms. Indicate whether this sample is n-type or p-type, and determine the thermal equilibrium hole and electron concentrations, p o and n o , respectively, in it and its electrostatic potential, f , realtive to intrinsic silicon. Show your work and/or o explain your answer. Type: ___________ _______ -3 p o = __________________ cm -3 n = __________________ cm o f = _________________ Volts o b) What are the diffusion lengths of holes and electrons, L h and L e , respectively, in the sample of Part a? Show your work and/or explain your answer. L
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This note was uploaded on 07/20/2009 for the course CSAIL 6.012 taught by Professor Prof.cliftonfonstadjr. during the Fall '03 term at MIT.

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01_exam1fall - Page 1 of 8 YOUR NAME_ Department of...

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