21. The top of the valence band is higher than the bottom of the conduction band in energy. 22. This condition is only satisfied in the conduction band, since the valence band is full in non-metals. 23. The hole is an empty state that allows electrons in the valence band some degree of freedom. 24. This energy corresponds to roughly the middle of the bandgap of Si, ~ 0.55eV above the valence band . 25. This is also applicable for electrons in the valence band ( often understood in terms of holes ). 26. Because the valence band is so nearly full, its electrons are not mobile, and cannot flow as electric current. 27. Most materials that conduct heat well have a valence band of free electrons which serve to transfer the heat. 28. The ionizing radiation produces electron-hole pairs : Electrons are in the conduction band and holes in the valence band . 29. This allows for free energy carriers in the conduction and valence bands thereby allowing greater conversion of photons to electrons. 30. Luminescence in a semiconductor results when an electron in the conduction band recombines with a hole in the valence band .
