Anomalous temperature dependence of optical emission in visible-light-emitting amorphous silicon quantum dots

Abstract

We have investigated optical properties of amorphous silicon quantum dots (a-Si QDs) embedded in a silicon nitride grown on (100) silicon substrates by plasma-enhanced chemical vapor deposition. The photoluminescence (PL) emission colors of red, orange, and blue were shown for the a-Si QDs with average dot sizes of 5.8, 2.4, and 1.3 nm, respectively. The increase in the PL peak energy with decreasing QD size was attributed to the quantum confinement effect in a-Si QDs. An anomalous temperature dependence of the PL intensity and PL peak energy was observed for a-Si QDs. The visible-light PL emission from a-Si QDs is most efficient at near room temperature, and the PL spectral shape and peak energy are almost independent of temperature, which are most favorable for light-emitting device applications. From time-resolved PL experiments, an enhancement of phonon-assisted indirect radiative recombination was proposed to explain the anomalous temperature dependence.