Light-induced effects on low energy photoluminescence in a-Si:H investigated by frequency-resolved spectroscopy

Light-induced creation of defects related to low energy photoluminescence in hydrogenated amorphous silicon

“…The intensity of the low energy PL, I LE , increases considerably after illumination as we have already reported [3], and sometimes becomes much larger than that obtained from a-Si:H films before illumination. In the case of curves Nos.…”

“…In the lifetime distribution of PL of E pl = 0.83 eV for all of the films before and after illumination, the peak at 1 ms is not seen and a broad component, which is attributed to a recombination of electrons trapped at radiative defects and self-trapped holes [3], is seen.…”

“…In the case of curves Nos. 1 and 2, the lifetime distribution is dominated by a narrow peak at 1 ms, which is attributed to the PL from triplet excitons trapped at defects [3]. In the case of curve No.…”

“…PL spectra in a-Si:H consist of a principal band peaked at 1.3-1.4 eV and low energy PL due to the radiative defects. Our recent studies of the lifetime distribution of the low energy PL suggest that the PL of 0.95 eV is dominated by emission from triplet excitons trapped at radiative defects, while that of 0.83 eV is dominated by emission due to recombination of electrons trapped at radiative defects and selftrapped holes [3]. Yamaguchi et al have proposed that the radiative defects responsible for the low energy PL are T þ 3 -N À 2 pairs, where T þ 3 and N À 2 denote a positively charged threefold coordinated silicon and a negatively charged twofold coordinated nitrogen contained as impurity, respectively [4,5].…”

“…The low energy PL increases in intensity after prolonged illumination, showing that there is light-induced creation of radiative defects in a-Si:H [3,6]. While these defects are created by illumination, there are native defects which exist in the a-Si:H films as grown, i.e., before illumination.…”