Interdiffusion in SiGe alloys with Ge contents of 25% and 50% studied by X‐ray reflectivity

Abstract

The interdiffusion in SiGe alloys has been studied by X-ray specular reflectivity using ex-situ and in-situ annealing experiments. We report on the evolution of the Ge profile of strain-compensated Si/SiGe multilayers due to high temperature annealing. These multilayers were grown pseudomorphically and strain-symmetrized on relaxed Si 0.75 Ge 0.25 and Si 0.5 Ge 0.5 pseudosubstrates by molecular beam epitaxy at 330 °C. The multilayer structures were annealed at several temperatures around 590 °C and around 800 °C. From modelling the X-ray specular reflectivity scans at various stages of the interdiffused structures, we obtained interdiffusion coefficients resulting in the activation energy and the prefactor for interdiffusion corresponding to Si 0.75 Ge 0.25 and Si 0.5 Ge 0.5 . The results obtained ex-situ for Si 0.5 Ge 0.5 and in-situ for Si 0.75 Ge 0.25 provide accurate values of diffusion parameters. 2442 M. Meduň a et al.: Interdiffusion in SiGe alloys with Ge contents of 25% and 50%

Interdiffusion in Ge rich SiGe/Ge multilayers studied by in situ diffraction

“…Both values E A and D 0 are strongly correlated so that the lower value of E A matches to the lower value of D 0 . Actually by comparing our results on x Ge = 0.7 and 0.9 with previously obtained ones by Ozguven and McIntyre 9 for x Ge = 0.9 as well as by those of 10, 13 for x Ge = 0.5, it turns out that the lower activation energies (around 2.9 eV) and prefactors (around 10 −2 cm 2 /s) are more likely for x Ge = 0.7 and the higher ones ( E A around 3.0 eV and D 0 around 10 0 cm 2 /s) are more likely for x Ge = 0.9. Due to the remaining uncertainty of the determination of the sample temperatures which was around 10 °C, the activation energy and diffusion prefactors cannot be obtained with sufficient precision so far since they turn out to be extremely sensitive to the slope of the diffusion coefficient as a function of 1/ T in an Arrhenius plot.…”

“…7–9 and references therein. The same values of activation energies and diffusion prefactors were obtained for samples with various MQW periods for layer thicknesses even down to 3 nm 10. At the moment, the experimental data on interdiffusion in SiGe alloys are available only for Ge contents x Ge < 0.5 whereas information on a sufficient parameter set for Ge rich SiGe alloys x Ge > 0.5 are missing apart from a first data set on x Ge = 0.91, published very recently 9.…”

“…Using Eq. (1) for Δ ρ with factor of 2 turns out to be quite accurate 10, 17. In this study, we use the first method for a straightforward peak analysis as well as the second one, i.e.…”

Interdiffusion in group IV semiconductor material systems: applications, research methods and discoveries

“…To avoid too much averaging over a large Ge range, the Ge molar fraction difference in each MQW is 0.05. With much larger Ge molar fraction differences from 0.15 to 0.80 in one period of MQWs, Meduna et al [98,99] investigated four xGe, average (from 0.25 to 0.90) and obtained similar interdiffusivity formulas to Aubertine's. Liu et al [100] measured it at xGe, average = 0.85 with a 𝑥 Ge difference of 0.35 in one period of MQWs.…”

“…The first approach uses high resolution X-ray diffraction (HRXRD) to probe multiple layered superlattice structures, which can also be considered as multiple quantum wells (MQWs). This approach was used by researchers such as Aubertine, Meduna, Ozguven and Liu et al [96][97][98][99][100].…”