Rare earth luminescence from rare earth doped silicon nanoclusters

Abstract

Rare earth luminescence from Si nanoclusters doped with RE ions for photonic applications is investigated. Er and Nd doped silicon rich silicon oxide (SRSO) thin films, which consist of Si nanoclusters embedded inside a $SiO_2$ matrix, were prepared by electron cyclotron resonance enhanced chemical vapor deposition with co-sputtering of rare-earth target. We find that the nanoscale structure of the SRSO films greatly influence the characteristics of the RE luminescence from RE doped SRSO films, and that the RE luminescence is dominated by RE ions located near the $Si/SiO_2$ interface that are excited via carriers generated in the Si nanoclusters. From the temperature and pump-power dependence of $Er^{3+}$ photoluminescence characteristics, we argue that the Er luminescence from properly optimized SRSO films are sufficiently efficient for practical applications. Detailed investigations of dependence of $Er^{3+}$ luminescence intensity and lifetime on pump pulse width indicate that the exciton-erbium coupling is dominant over carrier-exciton coupling, consistent with the above finding that the luminescent Er ions are at the interface between the Si nanoclusters and the $SiO_2$ matrix near the clusters. Luminescence properties of Nd-doped SRSO is similar to that of Er-doped SRSO, but the temperature dependence of $Nd^{3+}$ luminescence intensity is different from that of $Er^{3+}$ luminescence, an effect which we ascribe to its higher transition energy.