ENEE 313, Fall ’08 Midterm II Preparation1. Be able to solve the quizzes and homework problems.2. Make sure you retain a general knowledge of what we covered in the earlier parts of theclass, especially from Chapter 3. In particular, make sure you know about how to calculateequilibrium carrier concentrations and relate them to the location of the Fermi levels in bandenergy diagrams.3. From the book, read:(a) Chapter 4, sections 4.1, 4.2.1, 4.2.2, 4.3.1, 4.3.2, 4.4.1, 4.4.2, 4.4.3, 4.4.4.(b) Chapter 5, sections 5.2, 5.3, 5.4 (qualitatively), 5.5.1, 5.5.3 (qualitatively), 5.5.4, 5.6.2,5.74. Look through the self-quiz problems at the end of chapters.5. Equations you might need will b e provided.6. Know the methodology of the derivations we did in class.7. There will be true/false, multiple choice or fill-in-the-blanks questions about concepts anddefinitions.8. Some study questions:(a) What is tunneling? How and when can it happen?(b) What causes diffusion current? What causes drift current?(c) What is velocity saturation and how does it affect drift current?(d) What happens to the Fermi level when current is flowing? How is the Fermi levelarranged in a system when it is in equilibrium?(e) What do we mean by ”excess carriers?” What does the net carrier concentration in asemiconductor consist of?(f) What controls the generation rate? What controls the recombination rate for directrecombination?(g) What is the electron current direction given the electron particle flow direction? Whatis the hole current direction given the hole particle flow direction?(h) Given an electric field in the semiconductor, what happens to the band energy diagramrepresentation?(i) What do the terms in the current continuity equation represent?(j) What do the terms in the electron and hole diffusion equations represent?(k) What does the diffusion length (Lnor Lp) represent? How is it related to the diffusioncoefficient and the carrier lifetime?(l) What kind of an excess carrier profile is set up when there is a constant excess carrierinjection at one point of the semiconductor?1(m) How is the depletion region formed in a pn-junction?(n) How do we calculate the built-in potential?(o) How do we calculate the depletion region width at equilibrium? What is the relationshipbetween the depletion region widths and doping concentrations in the p- and n- regions?(p) What is the depletion approximation?(q) How do es the band diagram change when bias is applied to a pn-junction diode? Howdo the Fermi levels move relative to each other when bias is applied to one side?(r) How does the bias govern the net and excess minority carrier concentrations at thedepletion region edges on either side? How do these concentrations govern the current?(s) What controls the time-response of the current to changes in bias?(t) What makes a metal-semiconductor junction rectifying, ohmic or tunneling?9. Know about the following:(a) Fermi-Dirac distribution function, Fermi Level, definition and physical meaning(b) Doping: Donors, acceptors; extrinsic semiconductors: n-type and p-type; impurity com-pensation(c) Equilibrium hole and ele ctron concentrations in extrinsic semiconductors, relationshipsto dopant concentration and to each other(d) Law of mass action (n0p0= n2i) in equilibrium.(e) Conductivity, mobility, mean free time, average velocity of carriers in an electric field,drift current(f) Generation, recombination, recombination lifetime (minority carrier lifetime).(g) Direct and indirect recombination(h) Diffusion current, diffusion coefficient, the Einstein relation in equilibrium(i) Current continuity equation, carrier diffusion equations, excess carrier diffusion equa-tions, excess carrier diffusion in space(j) Depletion and bulk regions in the pn-junction diode(k) The built-in potential at equilibrium; at non-equilibrium, the effects of bias on the built-in potential and on depletion region width(l) Definitions of ”forward” and ”reverse” bias on a pn-junction(m) The relationship between majority and minority carrier concentrations (es pecially atdepletion region edge) , the built-in potential and the bias on either side(n) Derivation of the ideal diode current(o) Behaviour in reverse bias(p) Transient response, effects of carrier lifetime(q) Depletion (junction) and diffusion capacitances in a pn-junction(r) The ideality factor(s) Work factors and electron affinity of metals and sem iconductors(t) How to draw the band diagram of a metal-semiconductor junction at equiliibrium andidentify the junction