On thermal quenching of the photoconductivity in hydrogenated amorphous silicon

Study of anomalous behavior of steady state photoconductivity in highly crystallized undoped microcrystalline Si films

“…The structural investigations of our film reveal no trace of amorphous content and consequently, the material should exhibit low DB densities, it is therefore, difficult to link the observed TQ to just the DBs. However, another reason proposed for the TQ is the asymmetry in band tails in the gap, which seems to be more relevant here [9]. As seen in the results in the previous section, kT c < kT, and hence, Rose model could not be applied in this case to draw any rough sketch of DOS fit.…”

“…This is because, in case of separate causes for each of these findings, one cause may preclude the simultaneous occurrence of the other. TQ is a widely accepted phenomenon in a-Si:H and explained in terms of the transformation of recombination traffic from valence bond tail (VBT) states to dangling bonds (DB) [9]. The structural investigations of our film reveal no trace of amorphous content and consequently, the material should exhibit low DB densities, it is therefore, difficult to link the observed TQ to just the DBs.…”

“…The method employed is similar to Tran for a-Si:H [9], but with a modified DOS profile and parameters for lc-Si:H as reported by Balberg et al [10] except the values of l n ($10 cm 2 V À1 s À1 ) and l p ($0.5 cm 2 V À1 s À1 ). The effective DOS picture constructed for this type of fully crystallized material is shown in Fig.…”

“…Several numerical and experimental observations of the temperature and intensity dependence of steady state photoconductivity (SSPC) have been used to explain the physics of gap states over a wide range in the bandgap of a-Si:H [9], whereas SSPC on lc-Si:H films has not been explored much [8,10]. We have studied the opto-electronic properties of well characterized lc-Si:H films having varying degree of crystallinity by employing steady state photoconductivity measurements and tried to identify the role of microstructure in determining the electrical transport.…”

Recombination mechanisms in hydrogenated silicon nanocrystalline thin films

“…While the photocurrent generally increases with increasing temperature over a wide temperature range, a photocurrent decrease with increasing temperature is reported for some temperature regions. These results were explained in terms of a thermal quenching effect, in which valence band traps are converted to recombination centers under light illumination at some temperatures [4][5][6][7]. Metal contacts and the formation of metal silicide regions at the contact interfaces play an important role in determining these properties.…”