Photoluminescence lifetime distribution of a-Si:H and a-Ge:H expanded to nanosecond region using wide-band frequency-resolved spectroscopy

Coexistence of geminate and non-geminate recombination in a-Si:H and a-Ge:H observed by quadrature frequency resolved spectroscopy

“…A double-peaked lifetime distribution of PL consisting of the short-lived ($ls) and long-lived ($ms) components obtained by the QFRS, suggests the exciton recombination in a-Si:H [1] and a-Ge:H [2] at low temperatures T ; the short-and longlived components involve singlet and triplet excitons, respectively, under the geminate recombination condition for generation rate G 6 10 19 cm À3 s À1 . We further confirmed, by extending the QFRS to ns region, that no peak exists around ns in the lifetime distribution, and estimated the singlet-triplet exchange energy to be $40 meV for aSi:H from the PL spectra of the two components [3,4]. The geminate recombination model predicts the Gindependent lifetime distribution experimentally observed in a-Si:H under the geminate condition G 6 10 19 cm À3 s À1 [5]; hence steady-state carrier density n s should linearly depend on G in this model.…”

“…Films of undoped a-Ge:H with thickness $1.0 lm and defect density $1 · 10 16 cm À3 , and undoped a-Si:H with thickness $1.1 lm and defect density $2 · 10 16 cm À3 were deposited on Al substrates, as previously reported [2,3]. Spectrally integrated PL signals excited at 1.81 and 2.33 eV laser light were detected by Hamamatsu infrared photomultipliers (PMTs); the lowest energy of the PL detection was limited to $0.89 eV for a-Si:H and $0.73 eV for a-Ge:H. The optical system of f/1.0 optics was carefully designed to optimize the detection of PL signals by the PMTs.…”

Understanding the photoluminescence over 13-decade lifetime distribution in a-Si:H

“…QFRS spectra in the shorter lifetime range from $2 ns to $6 ls was measured by the dual-phase double lock-in (DPDL) QFRS technique [18]. The longer PL lifetime range from $1.6 ls to $160 s was measured using a digital lock-in amplifier with a low frequency limit of 1 mHz in the internal reference mode [15].…”

Luminescence from hydrogen‐free silicon nanostructures in amorphous hydrogenated silicon

“…The luminescence consists of a fast component with a decay time of 100 ns, a slow component of 2 ms with the strongest intensity and a luminescence component due to distant electron-hole pairs with the distributed life time [12,13]. It is often identified that the fast luminescence is due to singlet excitons and the slow luminescence due to triplet excitons [1,13]. The identification is incompatible with the localized band tail states in amorphous semiconductors.…”