Material characterization of high Sn-content, compressively-strained GeSn epitaxial films after rapid thermal processing

We report on the characterization of high Sn-content (∼10% Sn) GeSn films grown on (001) Ge/Si substrates using reduced-pressure chemical vapor deposition. Pseudomorphic 30 nm GeSn films were grown on relaxed Ge buffers, exhibit a smooth surface, and display strong photoluminescence (PL) with cavity-resonance fringes from the Ge buffer. Additional luminescence studies confirm that the measured PL originates from the GeSn film. A study on the effects of rapid thermal annealing is presented along with evidence of Sn surface segregation and formation of surface nanodots for anneals at 450 °C and above. Anneals at 400 °C for up to 500 s showed little change in PL intensity or material properties, which suggest that a critical temperature exists for post-growth thermal-processing of high Sn-content, compressively-strained GeSn films.

► Intense thermal treatments of Ge0.9Sn0.1 films result in Sn segregation effects. ► Post-growth fabrication processes of Ge0.9Sn0.1 should be kept at 400 °C or below. ► High-quality GeSn materials can be achieved without post-growth annealing. ► Post-growth annealing for high Sn-content films may not be necessary or useful. ► Low-energy PL peaks were experimentally confirmed to originate from GeSn.