Abstract
The structural and optical properties of erbium-doped silicon-rich silica samples containing of excess silicon and of erbium are studied as a function of annealing temperature in the range . Indirect excitation of ions is shown to be present for all annealing temperatures, including annealing temperatures well below for which no silicon nanocrystals are observed. Two distinct efficient transfer mechanisms responsible for excitation are identified: a fast transfer process involving isolated luminescence centers (LCs), and a slow transfer process involving excitation by quantum confined excitons inside Si nanocrystals. The LC-mediated excitation is shown to be the dominant excitation mechanism for all annealing temperatures. The presence of a LC-mediated excitation process is deduced from the observation of an annealing-temperature-independent excitation rate, a strong similarity between the LC and excitation spectra, as well as an excellent correspondence between the observed LC-related emission intensity and the derived excitation density for annealing temperatures in the range of . The proposed interpretation provides an alternative explanation for several observations existing in the literature.
- Received 8 August 2007
DOI:https://doi.org/10.1103/PhysRevB.76.195419
©2007 American Physical Society