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HL: Fachverband Halbleiterphysik

HL 33: Optical properties I

HL 33.6: Vortrag

Dienstag, 1. April 2014, 10:45–11:00, POT 006

Luminescence properties of Silicon nanocrystals excited with femtosecond laser pulses — •Friederike Albrecht¹, Daniel Hiller², Margit Zacharias², Jürgen Gutowski¹, and Tobias Voss¹ — ¹Institute of Solid State Physics, University of Bremen — ²Institute for Microsystems Engineering IMTEK, Faculty of Engineering, University of Freiburg

Silicon nanocrystals (Si-NCs) embedded in a SiO₂ matrix have been shown to be rather efficient light emitters as the relaxation of momentum conservation in the nanostructures substantially increases the radiative transition probability of electron-hole pairs compared to bulk silicon. Si-NCs are therefore promising building blocks for all-silicon based optoelectronic applications. Here, we study the luminescence and waveguiding properties of SiO₂-based optical ridge-waveguide structures with embedded Si-NCs as active layer (2nm < d_NC < 5nm) with the special emphasis on the generation and quantification of net optical gain. Under cw excitation with a HeCd-Laser at room temperature, a luminescence band centered between 700 and 850nm is observed. A blueshift of the photoluminescence is seen for decreasing Si-NC size because of the quantum confinement. To study the transient gain dynamics in the Si-NC waveguides, the samples were excited with the frequency-doubled output of a Ti:Sapphire femtosecond oscillator (Δ t<80 fs, λ=375nm). We will compare the luminescence spectra of the Si-NCs obtained under pulsed and cw excitation, discuss the excitation and recombination dynamics, and the possibility of achieving optical gain under fs-pulse excitation in the waveguide structures.