1415EEMv2resitexam1415

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1、SBCYEAR2ENGINEERING2014–2015ElectronicEngineeringMaterialsExaminationSessionTimeAllowedResit2hours10minutes(Including10minutesreadingtime)NOTE:Themarkforeachquestionisindicatedinsquarebrackets[].Thetotalmarkforthispaperis60.INSTRUCTIONSTOSTUDENTS·Noanswersmustbewritteni

2、nthefirst10minutes.·WriteyourCandidateNumberclearlyontheanswerbooksinthespaceprovided.·AnswerTHREEquestionsoutoffour.·Writeyouranswersintheanswerbooksprovided.Additionalsheetswillbeprovideduponrequest.·Nowrittenmaterialisallowedintheexaminationroom.·Nomobilephonesareall

3、owedintheexaminationroom.·Anapprovedcalculatormaybeusedintheexamination.UsefulFormulaeAllsymbolsnotspecificallydefinedhavetheirnormallyacceptedmeaningsUniversalConstantsk=1.38´10-23JK-1or8.62´10-5eVK-1q=1.6´10-19Cm0=4p´10-7Hm-1e0=8.85´10-12Fm-1h=6.62´10-34Jsme=9.1´10-31

4、kgMainEquationsIfneeded,assumethatthetemperatureis300Kunlessotherwisestated.AnswerTHREEQuestionsOnly.Question1(a)Forasemiconductordefinecarrierdriftandcarrierdiffusion.[4](b)i.SketchtheI-Vcharacteristicsforap-njunctionandexplainthedifferenceincurrentflowunderforwardandr

5、eversebias.ii.Statetwoexamplesoftheapplicationsofap-njunction.iii.Ifthesaturationcurrentofthep-njunctiondiodeis1*10-15A,whatisthereversecurrentbeforebreakdown?Isthemaincomponentofthiscurrentduetodriftordiffusion?Markthevalueforreversecurrentyouobtainedonthegraphyoudrewi

6、nQ1(b)(ii).[2][4][3](c)Drawanenergyleveldiagramforap-njunctioninthermalequilibrium.Onyourdiagramclearlylabelthedirectionsofelectrondrift,electrondiffusion,holedriftandholediffusion.[7]Question2(a)Definethefermi-diracdistributionfunctionandexplainhowitcanbeused.[3](b)i.W

7、hatisthepurposeofaddingdopanttosilicon?ii.Isboronann-typeorap-typedopant?iii.Intermsofelectronsandholesdescribewhathappenswhensiliconisdopedwithboron.[1][1][5](c)Asiliconingotisdopedwith1012boronatoms/cm3.FindthecarrierconcentrationandtheFermienergyatroomtemperature(30

8、0K).Theintrinsiccarrierconcentrationofsiliconis1.5*1010cm-3.Hint:drawabanddiagram.[10]Question3(a)i.Sketchtheo