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Practice Final Solution

# Practice Final Solution - Problem I(25 points Consider a...

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Unformatted text preview: Problem I (25 points) Consider a silicon pn junction with a cross—sectional area of 10'4 cm2 and the following parameters at T = 300K: N =1017cm_3,N =5x1015cm‘3,r =10_7s,r 210—63 d a p 72 pp 2 400 cm: / V.S, it" = 1000 cm; / VS a) (10 points) Sketch the thermal-equilibrium energy-band diagram across the pn junction. 1 b) (5 points) Determine the ratio of the hole current to total current at the space charge edge xn c) (5 points) Determine the ratio of the electron current to total current at the space charge edge —xp d) (5 points) Calculate the total number of excess electrons in the p region for Va=0.5V P U (I ) Drﬂ ‘? i ‘E h a? no \3 :1" 2%: _‘_ ELELEEE. T D? Air 99“.““(3 1 Ln DP i>In0 Problem 2 (25 points) Consider an Si pnp transistor with NE= 21‘11017 cm'3, N3 = 2x1016 cm'3, NC = 2xlO15 cm'3. The metallurgical base width is 1 um and the base cross sectional area is 10 mm. Assume the critical ﬁeld to be equal to 105 V/cm. a? ni =1.5x1010 0114,83 =11.7x 8.854x10‘14F/cm a) (5 points) Draw the energy band diagram under equilibrium. b) (5 points) Sketch the electric ﬁeld, charge density, and determine the potential between the emitter and collector. c) (5 points) For VEB = 0.7V, VEC : 2.0V, draw the excess minority carrier densities across the emitter, base, and collector regions. (1) (5 points) Determine the total number of excess holes in the undepleted part of the base. e) (5 points) Determine the common-base breakdown voltage. (AM Problem 3 (25 points) A MOSFET has the following parameters: 0 l p+ poly gate, r =100A,N =1016cm‘3,QSS =1011cm‘2 0x A n: =1.5x1l)‘0 01114, 60 = 3.9x8.854x10‘14 F/cm as =11.7x78.854x10‘14 F/cm QSS is the number of electronic charges per unit area in the oxide a) (10 points) Determine the threshold voltage. b) (5 points) Is the device enhancement or depletion type? Explain. c) (10 points) What type of implant and dose are required such that VT = 1V hi “L CF53" ”MI—RT; _ﬂ E3 _ L —' e M5... Te \qDFF-i l0 V l 5:0 ,_,835 6%) {golSXJ/‘ﬂ M ’9 FF“ 10 5,1\/ AH epms: "’2‘— ” / C ﬁgg: (2:1; __;‘_‘_— ‘ ex” ,3 VPB -_; CPMS" CW 2 315 IE; sz louxe. Cox: ' VFBZ “ZZngu’ aghSKlEJ’ \l 7., OW‘EV F5 [if \J N: F6 +2} ChJ'l’ 7 A L |.%\ :35 lame. 13.43 2X! 8 4 x K_ ‘53)], .1. __ , ZéSeNa __ 7‘” cox '"' are; \$51” “. Problem 4 (25 points). Consider an n-channel MOSFET at T=3 00K. Assume: 1 5 2 cm_3,Q =1011cm“ o 11* polysilicon gate, t =500A,N 22x10 a SS 0x W = Sym,L =1,um,,un :IOOO-EHLﬁM =3.9£ﬂ, - .s 80 = 8.854x10'l4F/cm QSS is the number of electronic charges per unit area in the oxide a) (10 points) Determine the threshold voltage. b) (5 points) Is the transistor enhancement or depletion mode? Explain. c) (10 points) Assume the transistor is biased in the saturation region, plot @ _ versus VGs for VSB=0 and Vsn=3 V. KT L“ (’71 , J __ Ei— > ,. 1:. / “-59” a.) Ciymé ‘ 16 +‘ qFPi- ) a]??? 6’ QQBWK ,,.. 0&5 Cir” ,“9 «3’ €16 (56+ ) CFE—Bﬂxg ﬁltlgouo v M ' _._, ’ Ci) : _. 9355 5 (0‘6 MS 7 (D55 w.._,355«— 'wae '2: “-i’ OgéV Vpg :: (Rug _ (OK 62110"? 7, :: 02932,in : 2X1L'9xs'35916'uxLé'lé'ch111:5 :, 3%? QA is»? ’62“ \Lrnl : VFB +21%} +7dli¢ﬁit al.036Jr1x-2a54r43’134r‘2s ...
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Practice Final Solution - Problem I(25 points Consider a...

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