Luminescence gap in hydrogenated amorphous silicon

Imaging the Thickness of Passivation Layers for Crystalline Silicon with Micron‐Scale Spatial Resolution Using Spectral Photoluminescence

“…In Figure , the full width at half maximum (FWHM) of the spectra is ≈150 meV, whereas that of c‐Si is ≈25 meV at 80 K . This broadening stems from the fact that the PL spectra from a‐Si:H and SiN are reported to be emitted by the carriers trapped at band‐tail states at the band edges, resulting in a relatively broad range of energies, rather than being emitted from the two sharp band edges, as is the case for c‐Si. In addition, various deposition conditions can yield various peak locations of the spectra.…”

“…For many decades, luminescence spectra from a‐Si:H and SiN have been investigated intensively regarding their spectral shapes, peak locations, and relative intensities under different measurement conditions and with various preparation conditions and techniques . A notable feature is that at low temperatures their spectra are much broader than those of c‐Si.…”

“…Furthermore, the PL peaks from the passivation layer and the substrate have distinctly different temperature dependences. At room temperature, the luminescence from the a‐Si:H passivation layer is quenched significantly, whereas the spectrum from the c‐Si substrate is broadened . As such, the spectrum from the passivated wafer is entirely dominated by the band‐to‐band emission from the substrate, as shown in Figure b.…”

Luminescence Gap in Regioregular Poly(3-hexylthiophene) Film

“…In the case of hydrogenated amorphous silicon (a-Si:H), electron-hole pairs excited deeply in the bands relax in the extended states by emitting phonons, then relax in the localized band tail states by hopping between localized band tail states, finally reach a definite localized band tail state at which the density is too low to make the hopping relaxation, and recombine radiatively to emit the luminescence with a constant peak energy [7]. On the other hand, the electron-hole pairs created at the localized band tail states lower than the definite band tail state by the low energy excitation recombine radiatively without the hopping relaxation.…”

“…Therefore, the peak energy of the luminescence induced with the low energy excitation decreases with decreasing excitation energy. The excitation energy at which the luminescence peak energy changes from constant to decreasing, names the luminescence gap [7].…”