Ultrafast photoluminescence dynamics of nitride-passivated silicon nanocrystals using the variable stripe length technique

Abstract

The ultrafast photoluminescence dynamics of nitride-passivated silicon nanocrystals is investigated using the variable stripe length geometry with 200 femtosecond pump pulses. We find that the luminescence lifetimes are in the nanosecond range throughout the entire spectral range. However, no evidence for optical gain is observed even when the pump fluence is in excess of 40mJ∕cm2. A comparison with similarly prepared, oxide-passivated silicon nanocrystals suggests that oxide passivation plays an important role in providing optical gain from silicon nanocrystals.

Nanosilicon photonics

“…Photoluminescence from nitride-passivated Si-nc has become worthy of attention because of the smaller bandgap than silicon oxide that is in favor of a better carrier injection and thus of more efficient electroluminescence [118,119]. However, despite the fast luminescence decay (ns) and the possibility of tuning the emission in the blue, considerations on the overall luminescence dynamics and the strong optical losses argue against the possibility of obtaining net optical gain [120].…”

Time-resolved photoluminescence spectroscopy of the initial oxidation stage of small silicon nanocrystals

“…Trapped carriers are spatially separated, which may lead to a lower probability of the Auger recombination. 14 Thus, these oxygen-related states may also play a crucial role in the observation of positive optical gain, 15 however, this effect has not yet been fully understood.…”

Intrinsic optical gain of ultrathin silicon quantum wells from first-principles calculations

“…While Pavesi et al 3 reported that the silicon nanocrystal has a net optical gain, the origin of that gain is considered to be extrinsic, i.e., defects due to the oxide passivation. 7 Therefore, whether intrinsic optical gains by silicon nanostructures are attainable or not is still an unsolved question.…”