Question

Consider a silicon device (which happens to be an npn bipolar transistor) with an emitter doping of 10^17/cm3, a base doping of 8x10^15/cm3 and a collector doping of 2x10^15/cm3.

Carefully calculate how the band diagram, charge density, electric field and electrostatic potential as a function of distance for this device changes from the equilibrium case when this bipolar transistor is properly biased to work as an amplifier. In other words, show how the band diagram changes when the emitter-base junction is forward biased and the base-collector junction is reverse biased. (For this bias plot, make your own assumptions for the forward and reverse voltages.)

Answer 1

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