Dynamics of high quantum efficiency photoluminescence from N-Si-O bonding states in oxygenated amorphous silicon nitride films

Abstract

We have reported high internal quantum efficiency (IQE) (∼60%) of photoluminescence (PL) at 470 nm wavelength from oxygenated amorphous silicon nitride (a-SiNx:O) films. In this work, we explored the dynamics of high PL IQE from luminescent N-Si-O bonding states in a-SiNx:O films by using a combination of time resolved PL (TRPL) and temperature dependent PL (TDPL) measurements. The TRPL measurements include time integrated PL, microsecond range PL, and nanosecond range PL measurement modes. The a-SiNx:O films exhibit ns PL decay dynamics that is independent of pumping fluence (WPF) and uniform across the PL spectrum, which is different from the PL decay behavior in a-SiNx films. Particularly, we precisely monitored the temporal evolution of the PL spectra profile to verify that the luminescent N-Si-O bonding states are responsible for the observed blue PL with a radiative recombination rate of ∼108 s−1. Such very fast radiative recombination rate can be compared with that in direct band gap CdSe nanocrystals and can also help us to understand the high PL IQE in a-SiNx:O films. Moreover, by combining the TD-PL lifetimes with the PL IQE values, the temperature dependence of radiative and nonradiative lifetime can be determined.