We present the microstructural evolution in Ge-rich ${\text{SiO}}_2$ doped with Er under different fabrication conditions. At sufficiently high Er contents and annealing temperatures, the ${\text{Er}}_2{\text{O}}_3$ and ${\text{Er}}_2{\text{Ge}}_2{\text{O}}_7$ phases are eventually formed, leading to an electroluminescence quenching of Ge-related oxygen-deficiency centers. The correlation between the microstructure and electroluminescence is discussed based on: (i) an Er doping dependent fragmentation/amorphization of Ge nanocrystals, (ii) a temperature dependent Ge diffusion toward the $\text{Si}/{\text{SiO}}_2$ interface, and (iii) the formation of different Er phases.

• Received 16 February 2009

DOI:https://doi.org/10.1103/PhysRevB.79.161302