Extension of Germanium-on-insulator optical absorption edge using CMOS-compatible silicon nitride stressor

Numerical study on the effect of an external stressor material, silicon nitride (SiN), on the tensile strain enhancement of Germanium waveguide-on-insulator (Ge WG-OI) was performed. The enhanced tensile strain shrinks Ge bandgap which leads to extension of optical absorption edge towards longer wavelength. It was found that 1GPa tensile SiN (400nm) would introduce ~0.65% uniaxial tensile strain (along WG width direction) in Ge WG with 0.5μm width and extend the Γ-valley-light-hole absorption edge to ~1658nm. Tensile strain-enhanced Ge WG-OI was also experimentally demonstrated. These studies pave the way for an on-chip tensile-strained Ge photodetector with improved performance comparable to InGaAs-based detectors. This technique is completely CMOS-compatible and could also be applied to other Ge-based on-chip active device design such as lasers.