Semiconductor physics is of obvious importance, as it

STUDY QUESTIONS
1. What is the most important bandstructure features of semiconductors? How many valence
and conduction bands do they have?
2. What is the difference between a direct and an indirect bandgap?
3. Consider optical absorption in semiconductors with a direct and indirect band gap. How is
wave vector and energy conserved in an indirect electronic transition?
4. What is the relation between the numberof electrons and holes in an intrinsic
semiconductor? Where is the chemical potential at T=0?
5. One can dope a semiconductor with an impurity (donor) having one electron more than the
semiconductor. What happens to the extra electron? In which state and at which energy is it
situated in a band structure scheme?
6. Do the same for acceptor doping (p-doping).
7. Calculate the ionization energy for a donor electron with effective mass 0.1 of the electron
mass and a dielectric permittivity of 10.
8. What happens if a semiconductor is doped with equal amounts of both donors and
acceptors?
9. State the condition of neutrality for a donor doped semiconductor.
10. How can you obtain a value of the band gap from a suitable plot of the electrical
conductivity? Sketch!
11. How can you obtain the ionization energy of a dopant from the same plot?
12. How can you obtain the doping concentration if the mobility is known?