X-ray microdiffraction investigation of crystallinity and strain relaxation in Ge thin lines selectively grown on Si(0 0 1) substrates

We used X-ray microdiffraction (XRMD) to investigate the crystallinity and strain relaxation of Ge thin lines with widths of 100, 200, 500 and 1000 nm selectively grown on Si(0 0 1) substrates using a patterned SiO2 mask by chemical vapor deposition. The variations of the strain relaxation in the line and width directions were also investigated in Ge thin lines with a width of 100 nm. After growth, crystal domains with very small tilt angles were detected in Ge lines with all four line widths. The tilt angle range was larger in thinner Ge lines. After annealing at 700 °C, the formation of a single, large domain with a specific tilt angle was detected by XRMD for Ge thin lines with widths of 100 and 200 nm. These experimental results reflect the effects of SiO2 side walls around the Ge thin lines on crystallinity and strain relaxation of Ge.

Research highlights► Selective growth of Ge thin lines with widths of 100, 200, 500 and 1000 nm on Si substrates. ► Crystal domains with small tilt angles exist in the as-grown Ge lines for the four line widths. ► The tilt angle range of the domain is larger in thinner Ge lines. ► Single domain with a specific tilt angle exists in 100- and 200- nm width Ge lines after annealing. ► SiO2 side walls around the Ge thin lines can affect crystallinity and strain relaxation of Ge.