Q1. Using the with as the HBT’s emitter, and the with as the base, the with as the collector. Given the electron affinity , band gap is , the electron affinity , and band gap is . Use Vegard’s Law to calculate the electron affinities and bandgaps of the base and collector materials. Calculate the conduction band offset and valence band offset between the emitter and base.
Q2. Draw the energy band diagram for the HBT at thermal equilibrium. And give out the built in potential of emmitter-base junction and base-collector junction. And draw the direction of built-in electric fields.
Q3. For the HBT, the emitter-base junction is forward-biased by and the base-collector junction is reverse-biased by . Draw the energy band diagram under these bias conditions.