K. Hattori et al., Tunneling-assisted thermalization and recombination of nonequilibrium carriers in localized states: Application to the frequency-resolved drift mobility in amorphous silicon - art. no. 125208, PHYS REV B, 6412(12), 2001, pp. 5208
This article presents a theory for nonequilibrium carrier kinetics in amorp
hous semiconductors containing localized states among which finite interact
ions are allowed via tunneling. Fourier domain solutions are explored inten
sively in order to quantitatively interpret the frequency-dependent photoca
rrier drift mobility determined by modulated photoconductivity measurement.
The theoretical analysis is in agreement with experiments carried out for
hydrogenated amorphous silicon over a wide range of frequencies and tempera
tures, and discloses that the inclusion of tunneling transitions considerab
ly accelerates carrier thermalization in localized band-tail states. A gene
ralized recombination model that considers both direct capture of band carr
iers and tunneling transfer of band-tail carriers into recombination center
s is also discussed in detail, suggesting that even for room temperature, t
he tunneling recombination takes place preferentially.