Q1. A. State Heisenberg’s uncertainty principle. Drive expression for wavelength through de Brouglie equation. B. Interpret the Blackbody Radiation Phenomena. Also explain the photoelectric effect with the help of neat diagram. eye A. Define a Semiconductor and classify its types. Explain why extrinsic semiconductors are required? B. Describe Doping. Name two types of extrinsic semiconductors formed due to doping in Intrinsic semiconductors. Q3. A. Elaborate the Energy band theory with a diagram and how it is used to classify various elements. B. Draw the energy band diagram of extrinsic and intrinsic semiconductors. C. Illustrate the energy bands of Gallium Arsenide and silicon. Q4. Explain e-k diagram. Give the significance of e-k diagrams. Q5. Define Fermi Level. TREE EEEQ6. Interpret the significance of designing of resistors. Q7. Interpret semiconductors being negative Tan Ue Reelin mel Cirle Ya Q8. Discuss 1. Drift Current, 2. Diffusion Current, 3. Mobility, 4. Resistivity 5. sheet resistance. Add these in above definition. [Contrast between diffusion current and drift current? State the relation between resistivity and mobility. Classify the significance of sheet resistance] Q9. Write down the expression for drift and diffusion current. In a P type silicon sample the hole concentration is 2.25x10"15/cm. what is electron concentration. Q10. When atoms share electrons, what type of bonding it is called? Q11. What is the atomic structure of silicon? Q12. How can you classify solids on the basis of conductivity? Give examples also. Q13. How can you describe the concepts of quantum mechanics that are imp for the study of semiconductors?|| Heisenberg Uncertainty Priavelpole, — ee toes thok jt 4s imsbevible te’ meamre _ oy tole. early tooth positten and i arene ay On ob fet" Thin peda foto to bord or _Nowe- particle duality ef mother + 7 _ dn field of 9 uomdwn ame chavics , impllcation A; Um eettatn ity _ princi ple jo_thek jt & 5 lanpertble to acuurikely measure eney Oh nytem tn done finite amntirnch, Of, Be a Me tam kenety Position 0% mgmentum nceuntely beth net eth Abmbinn court. eI yo err ' Zz. Sp eit In ao a bp = AL bP nei ° Un bx erwe bn powton l mm earre Mme Alo know that, pny hou- Amv 2 Se UK fa i => ear in Sx. Am: BV 2A. LAV tyro | “” UK rproarnurerntd of velo uty ee a ea Unrm Ant apd <4 A2%-BV = LO. m apt andDe Broglie Squat en This universe 4 rettty: Since vaddatt i Riogic — Cenclunded J yroture yod jak en ound bucotse —™ to __ De Broxic . a actos a tare senctinne nov, ponticle - die bs elated — tuith De Broglie _hlave According 2 Plank’s Quarta —___ the. energy ef the _pheten having — ry! & aavelength A" do _given_egs E-hy — ~ fee, to Ewitein’s man energy elation : i fe mt —© Le velouity ef Light, & B i y From 9, 0 % A> Ne get i x mete AV +} x : Ee 2 | 4 4 mC h £ 5 1 mos A A [a> A i ime | Since mC. = P= mompcduimn of ppheton. => de A ep 5 i t i Ty imstend of Phalion, bie Anve ox mackerdal fortide Of meus tan” _anaving with _vetodty fay then _P2 mV =|Black body Rodation 2 A Hack body tr Akal ore thet obsovbs all Khe vediation® (ght) tha Hrikes fk To sloy In thermal equilibyium , Ih mut eit redia- tm ab Dame vale os It obsorbt, th Ty a black body aio yodlates tu) fouy elicd taith a tempevatuve obove fhe absolte zevo , Cmits Light af alt the object por (eekly black ( fleck amy Ugh), Uren tlateints Hight: that come fem st da talled black b radiotion. Lvompe.» Filament of Ug but heating ment 4 boller; ony abfed that give of “AN mim omar tf ener ab abyelite Ze Lea: bw teamed as bhaue bedy yodi ot.64 - ———e The _Phaoetectte, Efjed + t Accowtny to quantum thao vy, Sighs I form of packets of energy — Caled photo Mois the phenomenon “of Crristen of jin bn Nhe le clon, from Ue medal suwfau tahoe “gb | j dadiation ef Aruitoble frequency fed) tr them tho emsllal elocluors ave old pbsito— | electrons ond the cunient 40 produced (ds collet Pholo elect curren 2 MO dobytances ) neta , a4 Me ay mene nutes gle oud electyens tthen — expord (0 vodlations of rtlable Wavelength + Light of Ath cherter’ waveleneh has more energy and & thes more efheuive In producing ° the. phate electrons Photoelectric effet tas discovered by Halluiachs ors Aucessfutly explained thvovelically fy Etarteln-What Are Semiconductor: A semiconductor material is defined by its ability to conduct electricity and its conductivity properties lie between conductor Eile} insulator. Under specific conditions, Semiconductors have the ability to act either as a pure conductor or a pure insulator. Moreover, semiconductors(after creating a PN junction) can also control the direction of the flow of electrical charges, which is not the case with conductors(as they allow current to flow in both directions).What is a Semiconductor? @P> A semiconductor is a materi @> Semiconductor Examples are: whose conductivity properties lie between the conductor and insulator. icon, Germanium, Gallium Arsenide etc. tts asa eS Semiconductor | a a Extrinsic a Uiveheit co stands for negative (free electrons) @> “p" stands for positive (holes)Instrinsic semiconductor Extrinste semiconductor (1) | It is a tetravalent pure erystal. (1) | It is the tetravalent crystals with impurity of th third and fourth group of periodic table. (2) | Its electrical conductivity Is low, (2)| Its electrical conductivity is high. (3) | Its electrical conductivity depends on (3) | Its electrical conductivity depends on the temperature, temperature plus the amount af doping impurity. (4) | Ata given temperature the number of (4) | The -type semiconductor have a majority charg free electrons and the number of holes cartier elecirons and p-type semiconductor hav fare equal. @ majority charge carrier holes. 2, = my, 2. In n-type n, > n, and in p-type n, < My,Energy band theory in solids Ina single isolated atom, the electrons in each orbit have definite energy associated with it. But in case of all the atoms are close to each other, so the energy levels of outermost orbit electrons are affected by the neighboring atoms. The electrons in same orbit exhibits different energy levels. The grouping of this different energy levels is called energy band. The energy levels of inner orbit electrons are not much affected by the presence of neighboring atoms. Important energy bands in solids Band energy The conduction band electrons are not bound to the nucleus of ator. The energy associated with forbidden band is called energy Forbidden gp gap and it is measured in unit electron volt (eV). electrons present in the valence bane are loosely bound to the nucleus of atom Classification of materials based on forbidden gap +Insulators The materials which does not allow the flow of electric current through them are called as insulators. Insulators are also called as poor conductors of electricity. Empty conduction band Band energy a Forbidden gap Around ISev Electron Full valence Rubber, wood, diamond, plastic are some examples of insulators.Conductors The materials which easily allow the flow of electric current through them are called as conductors. Metals such as copper, silver, iron, aluminum etc. are good conductors of electricity. Band energy oe Almost full conduction band No forbidden gap {| Electron “Semiconductors The material which has electrical conductivity between that of a conductor and an insulator is called as semiconductor. Silicon, germanium and graphite are some examples of semiconductors. Band and ener8Y almost empty conduction band Forbidden gap ‘Almost full valence band Electron The resistance of semiconductor decreases with increase in temperature.Direct and Indirect Band Gap Semiconductors The band gap represents the minimum energy difference between the top of the valence band and the bottom of the conduction band, However, the top of the valence band and the bottom of the conduction band are not generally at the same value of the electron momentum. Ina direct band gap semiconductor, the top of the valence band and the bottom of the conduction band occur at the same value of momentum. essen Pang B S&S ban gap ses A “atfeereces ooo ‘a photon can provide the energy to produce an electron-hole pair. Each photon of energy £ has momentum p = E /¢, where cis the velocity of light. Momentum will be very small for a photon ‘A photon of energy £, where E, is the band gap energy, can produce an electron-hole pair in a direct band gap semiconductor quite easily, because the electron does not need to be given very much momentum. Inan indirect band gap semiconductor, the maximum energy of the valence band occurs at a different value of momentum to the minimum in the conduction band energy: band gap Energy an electron must also undergo a significant change in its momentum for a photon of energy E, to produce an electron-hole pair in an indirect band gap semiconductor. This is possible, but it requires such an electron to interact not only with the photon to gain energy, but also with a lattice vibration called a phonon in order te either gain or lose momentum. electron, a photon and a phonon ---- slow processEk-D! ram. == 4 Tes-Plas the band ! band diagram Akows The Convent onal efcctrical. and optical Propss dle need to gap encyoy ently a To kyew more cf ratien f aoniconducto? knew E-k diagiar a dm E-k diagsam alos Aw ctor material cha wey ste of -o — bartiuctar Aci ten material” : Bee 4 yheny the elationalip bw the eneray fe available feds Ustedties — for ig yracley ru i the energy + —— mromertiim 0h the electoon iw Nhe Suk being mepmenttim and Eos Fiem_o. mathematical poidd of view 4 _ the hlaveve ctoy * 6 The Ek diogyam ‘the terri corr ductor 4 3 dbtetnel by valuing Schyoedingey's equation 4 =p liana of Ek _dlagvara. += Be: © Ek dingyan indtentes band gap (Cg), nthich a the dipper nce bn eneray between the top of Valence boned and _bettom off _cewtudfien bands. @® The _die-grom dimonstretter_ Electron (Kole) mobile © the diagram esplains. ekectron (hole) efpective mans:. @ the didgiam 2 io - = ; Shows — dhect versaw hadinect © The. dlagyan indicate, eas — the _ Akectey are _epvebly, et yk aoa she= Fermi Level and Fermi Energy “il Enrico Fermi, the physicist who first proposed Fermi level. It is imporlant in determining the electrical and thermal propertics of solids. ‘The term “Fermi level" comes from Fermi-Dirac statistics. which describes a distribution of particles over energy states in systems consisting of fermions (electrons) that obey the Pauli exclusion principle. temperature. Fermi level is also defined as the work done to add an electron to the system. in the band gap, approximately in the middle of In semiconductors the position of the Fermi level is the band gap. és Fermi level is the highest chergy state occupied by electrons in a material at absolute zero ‘The value of the Fermi level at absolute zero temperature (-273.15 °C) is known as the Fermi energy. Itis also the maximum kinetic encegy an electron can attain at T=OK, Fermi energy is constant for each solid, The Fermti energy is-a concept in quantum mechanics usually referring to the enorgy difference between the highest and lowest occupied single-particle statcs in a quantum systcm of nonsinteracting fermions at absolute zero temperature.Resistor colour code *Carbon Composition Resistor ~ Made of carbon dust or graphite paste, low wattage values ‘Film or Cermet Resistor - Made from conductive metal oxide paste, very low wattage values -Wire-wound Resistor ~ Metallic bodies for heatsin mounting, very high wattage ratings “Semiconductor Resistor ~ High frequency/precisic | surface mount thin film technology |What Is The Difference Between Positive And Negative Temperature Coefficients Of Resistance? + Temperature coefficients of resistance (TCR) can be positive or negative, influencing how materials react to temperature changes + Positive TCR materials, like metals, increase electrical resistance with tising temperature due to increased atomic vibrations leading to more electron collisions + Negative TCR materials, often semiconductors, show decreased electrical resistance as temperature i increases, thanks to more charge carriers and enhanced carrier mobility + The differences between positive and negative TCRs impact material selection, temperature compensation, and temperature sensing in ‘electrical engineering applications Resistance Change (Q) aR(+) are) J _————— Positive Slope Tempers —p Temperature —p i Memperature Negative change (C) Slope NTC Tharristr PIC Thrristr m.com |Diffusion current “The process by which, charge carers (electrons or hoes) in a semiconductor moves from a region of higher concentration toa region of lower concentration is called ciffusion. sin conerten en ten was oo 7s 7 e «, © ° . ow e e ° - ° eos 5, 0° |mm), 00 ze oF eo oo ke, o> we 55 ee vier aaanaroboeos coeanaion cortnaton on fen ‘Concentration gradient The diffusion curent density is rectly propertional to the concentration gradient. Concentration gracfent isthe difference in concentration of electrons holes ina given area. ‘The concentration gradient for n-type semiconductor is given by an hee Where = aftson cient dnsty due to i tlecrons ‘The concentration gradient for p-ype semizonductr is even by «i Ie ax 4 = fusion current deity due to holes an Jam 40D. Where 0, ithe citfuson coetcent of electrons ap Ip= ~ Doge Drift curent The flow of charge carro, which is due to the applied voltage or electric fed is elle ditt current. The average velocity that an electron or hole achieved — {due tothe applied voltage or elect ff called crift velocity & ft volocity of electrons VE HE itt volocity of holes rmobiity of electrons ¥ mobiity of holes pplied lect fil Te diftcament deny dus to ee lcs gen by | Se “ and the dit erent dry du oss en by “haem total eft extent density ‘The total current density due to elactzons isthe sum of drift and difusion currents. 4J,= Drift current + Diffusion current = Dsift current + Diffusion current ‘The total curent density due to electrons and holes is given by sclera,MODE The mobility of the electron is the drift velocity of the electron in presence of a unit amount of electric field. Mobility of holes is the ability of movement of holes in the semiconductor in presence of an external electric field. Why is the mobility of free electron greater than the mobility of hole? Resistivity is the opposite of conductivity, it’s a measure of how effectively a material slows down the flow of electricity. Insulators have a high resistivity rating. Materials such as metals and other conductors have a low resistivity rating. Poor conductiviy Good conductivily Good resiativity Poot reslativty Electricians use special tools with insulated oper haired handles made of materials with a high resistivity rating- Poor conductivity Good onducthity like rubber. Geodeesaivty Poorest Electrical Resistivity Electrical resistivity is the reciprocal of electrical conductivity. It is the measure of the ability of a material to ‘oppose the flow of current. ‘Metals are good conductors of electricity. Hence, they have low resistivity. The insulators like rubber, glass, graphite, plastics, etc. have very high resistivity when compared to the metallic conductors. “The third type is the semiconductor which comes in between the conductors and insulators. Their resistivity decreases with the increase in temperature andis also affected by the presence of impurities in them,> Increase the Length, flow of electrons impeded > Increase the cross-sectional Area, flow enhanced Sheet Resistance Rg -— R, is the resistance when W=L (unit of Rs in ohms/square) R,=2 t Sheet resistance (also known as surface resistance or surface resistivity) isa common electrical property used to characterise thin flms of conducting and semiconducting materials. It is a measure of the lateral resistance through a thin square of material, ie. the resistance between opposite sides of a square. The key advantage of sheet resistance over other resistance measurements is that it is independent of the size of the square - enabling an easy comparison between different samples. Another advantage is that it can be measured directly using a four-point probe.Atomic StructureElectrical Properties of solids Introduction to Electrical Properties Apart from general physical characteristics like density and rigidity, solids depict another important property called Conductivity. Conductivity is defined as the measure of a solid to ease the flow of electrons and conduct electricity. The values of conductivity are diverged and vary from 107° to 10’. The unit of conductivity is ohm! m° ‘ypes of Solids BAEC Rar iu aunty eck teursi hc) flow through them. Diets Matt suka gcse Cee * have low conductivities Le. they do not practically allow the électric circuit to flow through them * The electrical conductivity isin order 107° — 107 ohm* m* Brean neutered ANS Tens Tat pu ssi Beiter etic ator cue UL ae On the basis of conductivity solids are classified into three types, namely: + Conductors + Insulators + Semiconductors= ——= - expeeloll vole In Quamitim Mechamics Pier out: chor ond semi Ienportant 2 ss 7 quostum concerts Inpe : §sr semi conductor physics $ wy, mechanics, re abun Ohare Partick ty In een Lats pmntice Particles Vico. alec +h i ; (he and —taave like propertics « Tn semicerdus -ches, ‘this duatity explairs how — etectens cont hele behave: The wove — roture oh eh eee ina cemicorductor leads te the concept ah ae ekecrum — £nevgy bands: oat © _Scvodinger equation + Desevibes the me evel -tien of quantum. system, Crucial for Undeitonding 2techren behaviews bh Conicenductore © Energy boords avd bard gaps + Ta semicerdact0ys, the bond gap ty small, atlonting electrons 4p Jump from valence bank to cencluction. bons when exleted_ by thermal energy or externd — Infuences (like Photons) @ Fermi devel The Fermi devel in the energy level thad _ Rpernter _ecenpoied tates umoecupled — Stottes at obsolute zero temper z cakyres Tk plays a crucial vole fn deternale ning Aerial propucties , ot a Jiven E ene 9. (eval: . —© Aitten = Hole fpoivss- then om hecho bathe valence bord ds enitea 40 the conduction bond, Ht teaver behind a vacancy, Kno os hala: The tle tom ant ole pax tan move through. the mated ord contribute to eletolrad Conduct _ciity + The concept i evrentiol for Undue UT shat qeromtins —_mecharal.cr_ prado the frome: — rear 8 und ty Htondiovg tha —e of elect X04 germnlcondirctoyss Athith $s essential for ~anigdlag. ard __opthyizing _ dite cu Uke BIT, MOSFET, — Solon _1rlbo, diese, LED: ete,