1. Normalized plot of n 0 /N D as a function of temperature. This plot is for N D = 10 16 cm  3. Figure 2.20 2-20

2. Under high doping concentrations, the formerly discrete donor levels smear into a band, effectively narrowing the band gap by an amount  E g. Figure 2.21 2-21

3. Reduction of room-temperature band gap  E g as a function of donor density in phosphorus-doped silicon. Figure 2.23 2-23

4. The motion of an electron in a crystal. The electron changes direction randomly whenever it makes a collision. (a) Under no applied field there is no net progress in any particular direction. (b) When a field is applied, the electron tends to drift in some particular direction. A trajectory such as this would be found only under very high fields. Figure 3.1 3-1

5. 3-9 Mobility as a function of temperature. At low temperatures, impurity scattering dominates, but at high temperatures, lattice vibrations dominate. Figure 3.8

6. 3-10 The experimentally measured dependence of the drift velocity on the applied field. Figure 3.9

7. 3-13 Various generation and recombination processes. (a) An electron-hole pair is generated when an electron absorbs (in this case) a phonon plus a photon. This generation could also occur by the absorption of a single photon or multiple phonons. The photons and phonons are absorbed simultaneously. (b) Band-to-band recombination via the simultaneous emission of multiple phonons. (c) A two-step generation process, in which, for example, the electron absorbs a phonon to promote it to the acceptor state, then in the next step it absorbs a photon to go to the conduction band. (d) A typical recombination event in p-type material involves emission of a photon to take the electron temporarily to the acceptor level, then the subsequent emission of the phonon returns it to the valence band, annihilating a hole. (e) and (f) Recombination and generation via trap states. Figure 3.12

8. 3-14 (a) At equilibrium, electrons and holes are generated and destroyed at equal rates, thus maintaining some constant equilibrium n 0 and p 0. (b) When light shines on the sample, the photons can be absorbed, producing extra electron-hole pairs. Figure 3.13