High-field electron-drift measurements and the mobility edge in hydrogenated amorphous silicon

Abstract

We report electron photocarrier time-of-Sight measurements at high electric 6elds for two thick hydrogenated amorphous silicon (a-Si:H) pi nd-io-des. At 77 K an exponential increase in the electron mobility of more than 100 is observed as the field is increased to E = 400 kV/cm. The dispersion parameter was field independent. We discuss previous reports of field-dependent dispersion in terms of interface efFects. We propose a model for high-field efFects based on an electric jield de-pend-ent mo bility edge which accounts satisfactorily for the measured electric 6eld and temperature dependence of the electron drift mobility. ERective-temperature models do not account for our measurements since they predict field-dependent dispersion. The microscopic electron mobility po 3 cm /V s is remarkably independent of electric 6eld, temperature, and germanium alloying.

Exploring dark current voltage characteristics of micromorph silicon tandem cells with computer simulations

“…For higher values of F o the TRJ generates less e-h pairs due to field dependence of the cross sections present in Gu's model. 39 TABLE II. List of the electrical parameters of the TRJ structure.…”

“…37 Combining TAT with field dependent mobilities he could reproduce the measured J-V characteristics of tandem solar cells. 34 In a previous publication we studied the dark J-V curves of single n-i-p c-Si TRJ structures and the light J-V of a-Si tandem cells with different models available in the literature: 18 TAT, the Pool-Frenkel effect ͑PFE͒, 38 field dependent cross sections only ͑FDCSs͒, 37 and field dependent attempt to escape frequencies ͑FDAEF͒ following the work of Gu et al, 39 i.e., eff = o exp͑F / F o ͒. This last approach is equivalent to simultaneously assume field dependent free carrier mobilities and field dependent cross sections ͑or effective density of states N c and N v ͒.…”

Amorphous Silicon–Based Solar Cells

“…Remarkably, detailed analysis of drift-mobility measurements supports the concept of a well-defined bandedge [40,43]. Most workers consider the bandedge to be the energy that separates electron orbitals that are localized (i.e.…”

Hole Drift-Mobility Measurements and Multiple-Trapping in Microcrystalline Silicon

“…Yelon and Movaghar have suggested that multi-phonon effects lead to the variations, and this perspective has been applied by Chen, et al, to drift-mobility measurements [20]. Another possibility originating with highfield drift-mobility measurements in a-Si:H has been that ν reflects the bandedge density-ofstates g(E V ) [21], which suggests that the present measurements be interpreted as indicating a substantially lower value for g(E V ) in microcrystalline than in amorphous silicon. Plainly, we need more clues from experiment about the meaning of this parameter; it seems possible that its dramatic lowering in microcrystalline silicon could be providing it.…”