Figure 4

(a) Direct, indirect and Urbach energies (Edir, Eindir and EU, respectively) calculated for each studied sample. Lines are guides to the eye. (b) Proposed energy band diagram (Edir is an electron-hole recombination that results in photon emission, whereas Eindir free electrons have an indirect recombination that results in a low photon emission). Here is the multiphonon relaxation energy.