Theoretical investigation of tensile strained GeSn waveguide with Si3N4 liner stressor for mid-infrared detector and modulator applications

We theoretically investigate a tensile strained GeSn waveguide integrated with Si3N4 liner stressor for the applications in mid-infrared (MIR) detector and modulator. A substantial tensile strain is induced in a 1 x 1 mu m(2) GeSn waveguide by the expansion of 500 nm Si3N4 liner stressor and the contour plots of strain are simulated by the finite element simulation. Under the tensile strain, the direct bandgap E-G,E-Gamma of GeSn is significantly reduced by lowering the Gamma conduction valley in energy and lifting of degeneracy of valence bands. Absorption coefficients of tensile strained GeSn waveguides with different Sn compositions are calculated. As the Si3N4 liner stressor expands by 1%, the cut-off wavelengths of tensile strained Ge0.97Sn0.03, Ge0.95Sn0.05, and Ge0.90Sn0.10 waveguide photodetectors are extended to 2.32, 2.69, and 4.06 mu m, respectively. Tensile strained Ge0.90Sn0.10 waveguide electro-absorption modulator based on Franz-Keldysh (FK) effect is demonstrated in theory. External electric field dependence of cut-off wavelength and propagation loss of tensile strained Ge0.90Sn0.10 waveguide is observed, due to the FK effect. (C) 2015 Optical Society of America