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

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–Perot 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–Perot 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.

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