High-quality and homogeneous 200-mm GeOI wafers processed for high strain induction in Ge

The realization of efficient laser sources compatible with the microelectronics industry is currently one of the main challenges for silicon photonics. As Ge is CMOS compatible, the interest of using tensile strain or n-type doping to improve its light emission properties has significantly increased over the last few years. Theoretically, it has been predicted that the Ge bandgap becomes direct at around 4% strain for uniaxial tensile stress or 2% strain for bi-axial tensile stress. Several methods to induce such extreme levels of strain are currently investigated. The highest value of strain has been reached with Ge micro-bridges fabricated from Ge-On-Insulator (GeOI) substrates in a controllable and reproducible way. In this work we have first of all investigated the material properties of 200-mm GeOI wafers. Very high crystallographic quality is demonstrated at the micron-scale using Raman spectroscopy and synchrotron based Laue micro-diffraction performed at BM32-ESRF. We give then optimized designs of micro-bridge by comparing suspended and landed micro-bridges on different materials. We theoretically show that the thermal management is strongly improved in landed micro-bridges. Finally, we have developed specific processing for landing Ge micro-bridges on Si or SiO 2 , the photoluminescence measurements performed on landed micro-bridges shows an improvement of the Ge light emission with strain.