Problem Set #10 ECEN 3320 Spring 2021 Semiconductor Devices Due on April 7, 2021 1. Consider a silicon npn transistor with NE = 10 16/cm3, NB = 10 15/cm3, a channel area of 10−8 cm2 and emitter and...

Dummy


Problem Set #10 ECEN 3320 Spring 2021 Semiconductor Devices Due on April 7, 2021 1. Consider a silicon npn transistor with NE = 10 16/cm3, NB = 10 15/cm3, a channel area of 10−8 cm2 and emitter and base lengths wE = wB = 1µm. You can assume recombination currents are small compared with the emitter electron and hole current. Find: (a) the built-in potential, φi, across the base emitter junction, (b) the n and p side depletion widths, xn and xp, of the base emitter junction, (c) the IE,n,0 and IE,p,0, (d) the α and (e) the β. 2. We want to fabricate a high speed npn bipolar junction transistor (BJT) with a β = 100. The base is to be doped at NB = 10 16 cm−3 and the collector at NC = 10 14. The ratio of the emitter to base length, wE/wB, is required to be 11/32. High speed requires that the base is as thin as possible. Find: (a) the doping level that must be used in the emitter in order to satisfy the requirement that β = 100, (b) the minumum value for base length that we can use and still have the device operate as a transistor (that is, not be permeated by depletion regions), and (c) and the transit time for an electron to traverse the base, using the maximum electric field at the base emitter junction, EEB,max to find the drift velocity. 1