Semiconductor physics is of obvious importance, as it
Semiconductor physics is of obvious importance, as it
Semiconductor physics is of obvious importance, as it
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STUDY QUESTIONS<br />
1. What <strong>is</strong> the most important bandstructure features <strong>of</strong> semiconductors? How many valence<br />
and conduction bands do they have?<br />
2. What <strong>is</strong> the difference between a direct and an indirect bandgap?<br />
3. Consider optical absorption in semiconductors w<strong>it</strong>h a direct and indirect band gap. How <strong>is</strong><br />
wave vector and energy conserved in an indirect electronic trans<strong>it</strong>ion?<br />
4. What <strong>is</strong> the relation between the number<strong>of</strong> electrons and holes in an intrinsic<br />
semiconductor? Where <strong>is</strong> the chemical potential at T=0?<br />
5. One can dope a semiconductor w<strong>it</strong>h an impur<strong>it</strong>y (donor) having one electron more than the<br />
semiconductor. What happens to the extra electron? In which state and at which energy <strong>is</strong> <strong>it</strong><br />
s<strong>it</strong>uated in a band structure scheme?<br />
6. Do the same for acceptor doping (p-doping).<br />
7. Calculate the ionization energy for a donor electron w<strong>it</strong>h effective m<strong>as</strong>s 0.1 <strong>of</strong> the electron<br />
m<strong>as</strong>s and a dielectric perm<strong>it</strong>tiv<strong>it</strong>y <strong>of</strong> 10.<br />
8. What happens if a semiconductor <strong>is</strong> doped w<strong>it</strong>h equal amounts <strong>of</strong> both donors and<br />
acceptors?<br />
9. State the cond<strong>it</strong>ion <strong>of</strong> neutral<strong>it</strong>y for a donor doped semiconductor.<br />
10. How can you obtain a value <strong>of</strong> the band gap from a su<strong>it</strong>able plot <strong>of</strong> the electrical<br />
conductiv<strong>it</strong>y? Sketch!<br />
11. How can you obtain the ionization energy <strong>of</strong> a dopant from the same plot?<br />
12. How can you obtain the doping concentration if the mobil<strong>it</strong>y <strong>is</strong> known?