Scanning electron microscope (SEM) image of typical micro-structure (l = 20 μm, w = 2 μm) at three different fabrication steps: (a) micro-stripe definition upon window opening in to the SiN/Ge/SOI stack, (b) under-etching, and (c) after final trimming and detachment.
(a) Biaxial strain values (left axis) and measured Raman shift measured along the x-axis of two Ge microstructrures (l = 20 μm, center at x = 0) having width of 1 μm (circle) and w = 2 μm (square), after: defining a micro-stripe (blue markers), under-etching and releasing the micro-bridge from the substrate (red), and trimming the micro-bridge (green). The vertical dotted lines define the micro-structure length. (b) Displacement field calculated for a l = 20 μm long and w = 2 μm wide micro-stripe at its center (yz plane cross section at x = 0). (c) Biaxial strain and measured Raman shift as measured (square) or calculated (σSiN = −2 GPa blue line, σSiN = −3 GPa red line) in half microstripe l = 40 μm long and w = 2 μm wide. The origin x = 0 is set at the end of the edge of the microstripe, negative values correspond to measurements on the unpatterned region of the surface.
Raman shift and biaxial strain values in Ge at the center (a) and at the junction with the blanket stack (b) for different lengths l and widths w of a micro-stripe.
Results of FEM simulation on micro-stripes detached from the substrate: (a) three dimensional results showing the downward bending of the structure, (b) plane view, and c) cross section image of the calculated displacement field.
Biaxial strain values and measured Raman shift, at the edge of under-etched (dot) and trimmed (square) w = 2 μm wide micro-bridges as a function of the length l.
(a) RT PL of a micro-stripe (l = 60 μm, w = 5) measured at its center (top) and at the structure edge (bottom). The curves have been offset for clarity. (b) Photoluminescence of a trimmed micro-bridge (l = 40 μm, w = 2) measured close to the edge.
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