Semiconductor Electron-Hole Pair Creation Energies
The average energy to create an electron-hole pair as a function of bandgap energy for a selection of semiconductors. Two main bands are evident - the main branch found by Klein [J. Appl. Phys., 4 (1968) 2029] (solid line) and the n-VIIB branch (dashed-dotted line). The dotted line denotes the limiting case when εp=Eg. The difference between this curve and the measured curves is due to optical phonon losses and the residual kinetic energy left over from impact ionization thresholding effects.
Note the solid lines through the two branches are best fit "Klein functions" of the form 14/5 Eg + a1 in which a1 is a free parameter. In order to obtain good fits to both the main and secondary branches, both AlN and diamond were fit as part of the secondary branch because they are clearly displaced from the main branch. Note also, that while the parameter a1 = 0.6 for the main branch is reasonable, in that it should lie in the range 0 ≤ a1 ≤ 1.0, the fitted value for the secondary branch is unphysical.