Effect of self-patterned Si1-xGex template layer on the structural and optical properties of Ge dots

We report the structural and optical properties of Ge dots grown on self-patterned Si1-xGex template layers. The study focuses on the influence of a Si1-xGex template layer on Ge dot properties. Surface morphology is analyzed by atomic force microscopy and cross-sectional transmission electron microscopy. Optical properties are investigated by photoluminescence (PL) and Raman spectroscopy. The results show that increasing x in the Si1-xGex template layer from 0.3 to 0.5 induces a significant decrease of Ge island size and a dramatic reduction of Ge/Si intermixing. The lower intermixing is evidenced by the larger Ge-Ge/Si-Ge integrated intensity ratio of Raman peaks and by the island-related PL redshift. Moreover, the island-related PL signal is found to be highly dependent on the power excitation and temperature: from 10 to 30 K, an anomalous increase of islands' PL was accompanied by a rapid decrease of the wetting layer PL. Such a behavior results from the transfer of photon-induced carriers in the wetting layer into the neighboring islands. Significant PL signal at 1.55 mum was obtained up to room temperature for Si(001)/Si0.5Ge0.5/7 monolayer Ge structures. (C) 2005 American Vacuum. Society.