ece3080_old_exam1_solutions

# ece3080_old_exam1_solutions - ECE 3080 Semiconductor...

This preview shows pages 1–7. Sign up to view the full content.

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: ECE 3080 Semiconductor Devices Spring 2008 Dr. Klein Exam 1 SM‘DWQ Instructions: (1) Closed book, closed notes. You are only permitted a calculator and a writing instrument. (2) Show all work to receive full credit. Proctor will provide additional paper on request. (3) You have 105 minutes to work. Don’t get hung up on one problem. lfyou get stuck, move on and come back later. (4) Each problem is worth 20 points. (5) Circle, box, or otherwise indicate your ﬁnal answer. (6) Answers must be legible. (7) Calculate numerical values where possible. 1M 1. For this problem, the followin§ identity may be useful: sin (x) = 0.5 * (1 — cos(2 x)) (a) For a silicon quantum well of width W = 100 A, ﬁnd the proper normalization constant C; for the lowest (n = 1) conduction band bound state in the well. em m sin-av in: (es—3’7” We \poJK . ‘ g is We Sac} “M6 13700?“ : C0090 ‘” ‘09 (gilt-3B AK _M\ c} r 1 HM . 1‘; Z we HAT- C :0 wmév H’\ v \ ‘2) __ . .l i. (b) Find the probabilit of ﬁnding an elee o in the n = 1 state within 20 A of the center ofthe well. O.ﬁ m I" 5% Q: g zwcwg dxé ZS 2. Assume a material has conduction and valence bands given by Emma) = BC + El sin? (k a I 2) Evamk) = Ev cos2 (k 3,12) Let a = 0.5 nm, EC = 2.1 eV, E] = 3 eV, and Ev = l.OeV. (a) Roughly sketch the bandstructure (E vs. k) for both bands on the same set of axes. A / (In) Find the longest wavelength of light that can be absorbed Via an interband Optical transition in this material. 0 gram :‘ EL "- Ev 1 \«lﬂv (0) Does this material have a direct or an indirect bandgap? é QLQEQCXI 9 0 (d) Based on your answer to N, do you expect that this material will efﬁciently emit light? Brieﬂy explain the physical reason why or why not. .5 eg' «Q, Min 43K— ané. (IVE—"Q 9% Wu: W\Jrv\~\ L, a \$2 Max: u -~1'\~ \OD'AA- ’_;> We ~ MOMMHW‘ (Di/\o’rorx CW [at umk'oeh in H“; Jﬂ‘yxsi‘ih‘hﬂ (e) Find the hole effective mass. _ EM: QM) Cesium cam/a3 PWW}: Zlé’ défw- QA‘ Q LL: 0 g L?) weciebmk—e 2m -2: 239m *9 la. #53, “Lwii %SECOSZ(€B “‘ §macgsg 8. L2, : 0 919m at FAVE“ an} 1 * J71“ " W . z w» 5. wig. * genera kg 39 V 10 3. A diode has a ‘depietion region”, where we can approximate n = p = 0. Suppose a depletion region extending from x = 0 to x = W is uniformly doped with some constant acceptor concentration NA. Assume that the electrostatic potential (p and the electric ﬁeld E are both zero atx=0. Find E(x) and (p(x) for0<x<W. @ COCK: 03;; 0 E01; 03:“ O V End K ther I W 49 ='-* 80 Keen. M o : :- Ci'M.__“* 04X<VQ /0 kegox d Tif— : r E K " 1 S «W —-= -~ Voltaire“ /0 (9&3 7* £04; KL ©4x<w 4. Short answer. (3) Brieﬂy deﬁne the Fermi energy EF. we 6 94 £964 2, A Gig—Ia; Mg 660‘03‘0} 8F. :3 (b) Brieﬂy deﬁne the intrinsic level Ei. As you know, it is nearly in the middle of the bandgap, but not exactly. Why not? lg w EI— \ “week; we ii aw [ﬂiéw’r' deed- Q N 0% mm; m meme 0L 6G K Lav-9L Al :- (3; , ‘bo‘t' (143‘ 4 MU dedﬁ‘c’ﬁ (c) Brieﬂy explain the density of states, g. What does it represent? / é 30\$ ‘5 W a? gbgg/Qol X eweréj LA (“Jet L. AWUBK \$50M, SWa-kk m beLNKCK/ E: in Z/ \_ ((1) Brieﬂy explain the Auger recombination process. Whathappens in this process? A sketch might help. 5 : Z eiachro n3 4 t k 0 [EL [ Mac/Wan m 4m [no {a 4 W534 (6) Using the ﬁgure below, determine a semiconductor alloy that will have a bandgap of 1.8 eV, and can be grown on a GaAs substrate with a relatively small lattice mismatch. Provide the composition of this alloy in the standard notation. Bandgap (at!) {uni} umuagmm 52 5,4 5.6 5.8 5.9 8,2 5.4 8.8 Lattice constant {A} MUM“; Ql A19 °r 9“ ﬁring (ﬁgs RS ...
View Full Document

## This note was uploaded on 10/12/2010 for the course ECE 3080 taught by Professor Staff during the Spring '08 term at Georgia Tech.

### Page1 / 7

ece3080_old_exam1_solutions - ECE 3080 Semiconductor...

This preview shows document pages 1 - 7. Sign up to view the full document.

View Full Document
Ask a homework question - tutors are online