Problem 1. Nonideal effects There are two npn bipolar transistors that are same except the emitter and collector region doping are interchanged. Device A: NE=107 cm, NB = 105 cm, Nc = 1014 cm Device B: NE = 1014 cm, NB = 105 cm, Nc = 107 cm (a) Which transistor is expected to have larger emitter efficiency? Briefly explain. (b) Which transistor will be more sensitive to base width modulation under forward active mode biasing? Briefly explain. (c) If limited by avalanche breakdown in the BC junction, which transistor will have larger BVCBO? Briefly explain. Problem 2. Heterojunction Bipolar Transistor A npn HBT has a n-type emitter which bandgap is higher than the Si base and collector by 0.3 eV, where AEC = 0 and AE = 0.3 eV. Emitter doping is 107 cm and base doping is 5x109 cm 3 and collector doping is 107 cm. Assume equal effective masses, diffusion constants, lifetimes for the two materials, and XE = XB = 0.1 m, and room temperature (a) What is the emitter injection efficiency? (b) Calculate the depletion width extending into the base (XdB) from the BC junction at VBC = -2V (reverse bias). Is this HBT sensitive to base width modulation?