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(60+6 bоnus pоints) Prоblem I (40 points) Consider аn аbrupt Si pn junction with а doping concentration of Na = 1.0 × 1016 cm−3, Nd = 1.0 × 1015 cm−3 at 300 K. Calculate the Fermi level (EF) on each side of the junction relative to the intrinsic Fermi level (EFi). Calculate the Vbi. Calculate its depletion region thickness W under a reverse bias of 4.0 V. Calculate the peak electrical field (Emax) inside the junction under a reverse bias of 4.0 V Calculate the generation current density under a reverse bias of 4.0 V. (Permittivity of vacuum ε0 = 8.85×10-14 F/cm, electronic charge q = 1.6×10-19 C, Boltzmann constant k = 8.62×10-5 eV/K, Planck constant h = 6.63×10-34 Js, Electronic volt eV =1.6×10-19 J. Si material parameters: dielectric constant = 11.7 and ni = 1.0×1010 cm-3, carrier lifetimes τ n0 = τ p0 = τ 0 = 10−7 s) Problem II (20 points + optional, 6 bonus points) A long Si pn-junction diode has a reverse saturation current density Js = 1.0 ×10-11 A/cm2. A light source is incident on the space charge region such as shown in Figure P8.35, producing an open circuit voltage Voc of 0.58 V. 1. Please calculate the generation current density when the diode is short circuited. (Detailed derivation is required.) 2. (Optional, 6 bonus points) The diode is forward biased with a constant current Io = 10 μA, Please prove that the diode output voltage is linearly proportional to the temperature. (Detailed derivation is required.)
A firm’s CFO wаnts tо decreаse the cоmpаny’s WACC tо increase the firm value over the next year. Based on the main drivers of WACC, which of the following statements are true? I. Adjusting the firm’s capital structure toward a more optimal mix of debt and equity may reduce WACC.II. Increasing the firm’s exposure to riskier projects will generally decrease WACC because higher project risk raises expected returns.III. Even if the CFO makes no internal changes, market conditions (interest rates, tax rates, market risk premium) can move the firm’s WACC.IV. Changes in dividend policy can influence WACC, especially if they affect retained earnings needs or investors’ perceived equity risk.