Low-temperature transport and recombination in a-Si: H

Bandtails and defects in microcrystalline silicon (μc-Si:H)

“…The observed changes in the EDMR spectra suggest that there is a change of the recombination mechanism at TϷ40 K which is related to the pronounced enhancement of PH . This overal picture again strongly reminds of the behavior familiar from a-Si:H. 13,15 …”

“…The behavior of c-Si:H has pronounced similarity with that of a-Si:H, where at TϽ50 K, the concentration of light-induced electrons trapped in the cb tail and the photoconductivity increase with G following power laws with exponents of ␥ϭ0.15-0.2 and nϷ1, respectively. 12,13 The EDMR spectra exhibit a resonant decrease ͑quench-ing signal Q͒ of the photocurrent in the entire temperature interval of 5-300 K. The high value of the signal amplitude of ⌬/ϭϪ5ϫ10 Ϫ3 at Tϭ5 K suggests that we are dealing with a major recombination channel. This conclusion appears to be supported by the observation that ⌬/ does not depend on G. The shape of the EDMR signal changes considerably with T ͑Fig.…”

Recombination and transport through localized states in hydrogenated amorphous and microcrystalline silicon

“…However, surprisingly the influence of the electric field is far less pronounced. At the highest value F = 200 kV/cm the decrease of the photoluminescence (PL) intensity amounts to about 10% only [19]. This discrepancy may be taken as an indication that the effective-temperature approach does not apply in case of non-radiative recombination and that the transport energy does not determine the non-radiative recombination mechanism in a simple way.…”

“…When their density exceeds 10 17 cm À3 , the PL-intensity is strongly quenched. Reprinted with permission from [19]. of this strong quenching effect is non-radiative tunneling of electrons from the band tail into the defect states.…”

Experimental Evidence for the Applicability of an Effective Temperature Concept ina−Si:H

“…Thus, to a first order approximation the previous Teff = T + CT+'F~2, (8) here C is a constant that can be expressed in terms of localization length, electronic charge, and Boltzmann The localization length depends on the depth from the band edge as [6] 1 (E) =~o (Eo./E)'. (10) where ap = N / = 3 nm, N is the total density of conduction band-tail states in a-Si:H, and Ep is the inverse slope of the conduction band tail. So an increasing localization length implies decreasing localization of the electrons, which is consistent with the fact that with an increase in the generation rate, the quasi Fermi level moves toward the band edges, i.e.…”