Infrared tubular microcavity based on rolled-up GeSn/Ge nanomembranes

Germanium-Tin (GeSn) alloys have attracted great amounts of attention as these group IV semiconductors present direct band-gap behavior with high Sn content and are compatible with current complementary metal oxide semiconductor technology. In this work, three dimensional tubular GeSn/Ge micro-resonators with a diameter of around 7.3 μm were demonstrated by rolling up GeSn nanomembranes (NM) grown on a Ge-on-insulator wafer via molecular beam epitaxy. The microstructural properties of the resonators were carefully investigated and the strain distributions of the rolled-up GeSn/Ge microcavities along the radial direction were studied by utilizing micro-Raman spectroscopy with different excitation laser wavelengths. The values of the strains calculated from Raman shifts agree well with the theoretical prediction. Coupled with fiber tapers, as-fabricated devices present a high quality factor of up to 800 in the transmission spectral measurements. The micro-resonators fabricated via rolled-up nanotechnology and GeSn/Ge NMs in this work may have great potential in photonic micro- and nanodevices.