Study of the light emission in Ge layers and strained membranes on Si substrates

• High quality germanium layers were grown on Si or on SOI 200 mm wafers.
• Germanium membranes were fabricated to induce uniaxial and biaxial strains.
• We carefully examine changes in the light emission as function of the designs.

The influence of pattern design and tensile strain on light emission was investigated in Ge layers and suspended membranes. The optical properties were examined by micro-photoluminescence and reflectivity. Tensile strain was extracted from micro-Raman spectroscopy. It has been shown that Fabry–Pérot interference fringes can dominate the photoluminescence spectra. It is crucial to remove them in order to analyze the photoluminescence changes coming from tensile strain; especially if Fabry–Pérot oscillations are in the same energy range compared to the stress-induced spectral shift. This study highlights the fact that this interference must be taken into account in order to examine the strain in suspended Ge layers.