midtermF10

midtermF10 - Name/Perm No.: SOLUTIONS ECE 124AFall 2010...

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Name/Perm No.: SOLUTIONS ECE 124A–Fall 2010 Prof. K. Banerjee 1/11 UNIVERSITY OF CALIFORNIA, SANTA BARBARA Department of Electrical and Computer Engineering MIDTERM EXAMINATION-ECE124A Room: ESB-Cooper Lab, November 9, 3:30-5:30 PM READ CAREFULLY: This is a CLOSED BOOK Exam. Any form of notes is not allowed. Calculators OK. READ the questions carefully before answering. Include all your answers in locations specified on these pages. Show ALL WORKING used to arrive at answers. Use space provided for all working. Use the back sides if necessary. There are 10 pages including the cover page. Be sure to write Your NAME/Perm No. on EVERY PAGE. Question Scores #1 / 30 #2 / 35 #3 / 35 TOTAL / 100 Good Luck!
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Name/Perm No.: SOLUTIONS ECE 124A–Fall 2010 Prof. K. Banerjee 2/11 Useful Constants and Relations: 3 10 23 19 0 0 14 0 10 45 . 1 026 . 0 / 10 38 . 1 10 6 . 1 9 . 3 7 . 11 / 10 85 . 8 cm x n V q kT K J x k C x q cm F x i ox Si 1) n . p = n i 2  fn = kT/q ln (N d /n i ); fp = kT/q ln (n i /N a ) 1. (30 pts) VLSI Devices (suggested time: 30 minutes) i) (10 pts) The energy band diagram for a P-N junction silicon diode is shown below. a) Is side #1 n-type or p-type? Find the doping concentration. (3 pts) N-type since Fermi level is above E Fi . V q E E N N q kT i F FN i D FN 3 . 0 , ln Ln(N D /N i )=0.3V/0.026V N D =1.49 x 10 15 cm -3 b) Repeat for side #2. (2 pts) V q E E N N q kT i F FP A i FP 2 . 0 , ln Ln(N A /N i )=-0.2V/0.026V N A =3.18 x 10 13 cm -3 E V 0.2eV 0.3eV E C E F E i SIDE #1 SIDE #2
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Name/Perm No.: SOLUTIONS ECE 124A–Fall 2010 Prof. K. Banerjee 3/11 c) What is the voltage V F (from P to N) applied across this diode? (2 pts) V F =0 V since there is no difference in Fermi level at the two electrodes. d) What voltage V F should be applied in order to flatten the bands? (3 pts) V F =built-in voltage V 0 V 0 = Φ FN - Φ FP =0.3 V – (-0.2V) = 0.5 V ii) (5 pts) Sketch (qualitative only) the location of the Fermi level as a function of the doping concentration (from 10 13 to 10 20 ) in Si at 300K and 400 K. The y- axis should be energy in eV (indicate E C and E V ) and x-axis is dopant concentration (N a or N d ) in cm -3 . E C 300K 400K E F , donor doped Boltzmann approx. not valid 400K E F , acceptor doped 300K E V 10 13 10 14 10 15 10 16 10 17 10 18 10 19 10 20 N a or N d (cm -3 ) iii) (10 points) Consider the long channel NMOSFET structure shown below: G N+ poly gate S D ToxA ToxB L/2 N+ N+ P
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Name/Perm No.: SOLUTIONS ECE 124A–Fall 2010 Prof. K. Banerjee 4/11 T oxA =2 T oxB , The channel length is L, and Width is W. Assume Vt and mobility eff are constant throughout the channel. Assume Vgs=5V, Vt=1V, Vds=2V, Vbs=0.
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This note was uploaded on 12/04/2010 for the course ECE 134 taught by Professor York during the Fall '08 term at UCSB.

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midtermF10 - Name/Perm No.: SOLUTIONS ECE 124AFall 2010...

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