Raman shifts in MBE‐grown Si_xGe_{1 − x − y}Sn_y alloys with large Si content

Abstract

We examine the Raman shift in silicon-germanium-tin alloys with high silicon content grown on a germanium virtual substrate by molecular beam epitaxy.The Raman shifts of the three most prominent modes, Si-Si, Si-Ge, and Ge-Ge, are measured and compared with results in previous literature. We analyze and fit the dependence of the three modes on the composition and strain of the semiconductor alloys. We also demonstrate the calculation of the composition and strain of Si x Ge 1 − x − y Sn y from the Raman shifts alone, based on the fitted relationships. Our analysis extends previous results to samples lattice matched on Ge and with higher Si content than in prior comprehensive Raman analyses, thus making Raman measurements as a local, fast, and nondestructive characterization technique accessible for a wider compositional range of these ternary alloys for silicon-based photonic and microelectronic devices.

Synthesis of High Sn Content Ge1–x–ySixSny (0.1 < y < 0.22) Semiconductors on Si for MWIR Direct Band Gap Applications

“…In the original work of D’Costa, the shifts due to the external strain were accounted for using strain-coefficients measured in bulk Ge and Si as well as Ge 1– x Si x alloys . The same approach was used later by Fournier-Lupien and co-workers, but in more recent work, Schlipf et al attempted a global fit that includes the external strain coefficients as adjustable parameters . We find that the parameters recommended by Schlipf et al show somewhat better agreement with the experimental data in Figure , and we quote the predicted frequencies for our samples in Table .…”

“…35 The same approach was used later by Fournier-Lupien and co-workers, 39 but in more recent work, Schlipf et al attempted a global fit that includes the external strain coefficients as adjustable parameters. 40 We find that the parameters recommended by Schlipf et al show somewhat better agreement with the experimental data in Figure 15, and we quote the predicted frequencies for our samples in Table 3. The agreement is quite reasonable given the experimental uncertainties and the above-mentioned possible Si−Ge and Si−Sn peak merge.…”