Expanding the Ge emission wavelength to 2.25 μm with SixNy strain engineering

•Ge nanopillar structures were fabricated using electron beam lithography.•The structures were strained by silicon nitride stressor layers.•Photoluminescence was measured to determine the band-edge of the strained pillars.•Raman measurements were taken to confirm high levels of strain.•Finite element modelling was used to calculate strain distributions.

Photoluminescence up to 2.25 μm wavelength is demonstrated from Ge nanopillars strained by silicon nitride stressor layers. Tensile biaxial equivalent strains of up to ~ 1.35% and ~ 0.9% are shown from 200 × 200 nm, and 300 × 300 nm square top Ge pillars respectively. Strain in the latter is confirmed by Raman spectroscopy, and supported by finite element modelling, which gives an insight into the strain distribution and its effect on the band structure, in pillar structures fully coated by silicon nitride stressor layers.