121B_1_EE121B_2011MT01_v21-SOLUTIONS

121B_1_EE121B_2011MT01_v21-SOLUTIONS - EE 121B / Winter...

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EE 121B / Winter 2011 / Prof. Chui / UCLA Midterm Exam, p.1 EE 121B Principles of Semiconductor Device Design Winter 2011 Midterm Exam February 15 h , 2009, 2:10-3:50pm LHS Neighbor First Initial and Last Name (e.g. K. Smith): __________________________ Name : ____ Suggested Solutions ____ Student ID# : ____________________________ Signature : ____________________________ RHS Neighbor First Initial and Last Name (e.g. J. Smith): __________________________ FORMAT: - TOTAL: 100 POINTS - TIME ALLOTTED: 100 MINUTES - CLOSED BOOK - ONE PAGE OF LETTER SIZE SHEET OF NOTES AND A SCIENTIFIC POCKET CALCULATOR ALLOWED INSTRUCTIONS: - USE THE FOLLOWING PHYSICAL CONSTANTS AND GENERAL ASSUMPTIONS IF NECESSARY - SHOW ALL WORK AS CLEARLY AS POSSIBLE TO MAXIMIZE OPPORTUNITY FOR PARTIAL CERDIT - USE COMMON SENSE TO INTERPRET THE QUESTIONS, OR ASK IF YOU ARE NOT SURE - INSERT YOUR ONE PAGE NOTES INTO THE EXAM BOOKLET WHEN YOU TURN IN YOUR EXAM Physical constants: I. Electronic charge = 1.60 × 10 -19 C II. Vacuum Permittivity = 8.85 × 10 -14 F/cm III. Boltzmann constant = 8.62 × 10 -5 eV/K IV. Planck constant = 6.63 × 10 -34 J-s V. Electron mass in vacuum = 9.10 × 10 -31 kg General assumptions in all problems unless specifically stated otherwise: I. Temperature = 300 K Semiconductor = Silicon a. Intrinsic carrier concentration 1 × 10 10 cm -3 b. Permittivity = 11.8
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EE 121B / Winter 2011 / Prof. Chui / UCLA Midterm Exam, p.2 Questions: 1) {18 points} Multiple choices with no partial credits. Circle the correct answer. a) The electron velocity under random thermal motion in Si is closest to i) 10 3 cm/s ii) 10 5 cm/s iii) 10 7 cm/s iv) 10 9 cm/s b) The saturated drift velocity in Si is closest to i) 10 3 cm/s ii) 10 5 cm/s iii) 10 7 cm/s iv) 10 9 cm/s c) How does the PN junction built-in voltage change when we increase the ambient temperature from 300K to 1000K assuming the doping in both the P- and N-regions are not very heavy?
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121B_1_EE121B_2011MT01_v21-SOLUTIONS - EE 121B / Winter...

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