Non-linear bandgap strain dependence in highly strained germanium using strain redistribution in 200 mm GeOI wafers for laser applications

Summary form only given. Applying a large tensile strain of several percent in a Ge layer is promising in order to improve its optical properties and possibly turn germanium into an efficient CMOS compatible light emitter. Several approaches are currently being explored for high strain induction into Ge. Since biaxial or uniaxial stress inductions are interesting, we have studied both approachs using tensile strain redistribution in 200 mm GeOI wafers. In this work, we compare simulations with experimental results in order to accurately investigate the bandgap-strain dependence in highly strained Ge devices. In order to carefully measure the bandgap-strain dependence, photoluminescence and electro-absorption measurement were performed and compared to strain characterizations by micro-Raman spectroscopy and synchrotron based micro-diffraction at the BM32 beamline of ESRF Grenoble. Due to the high crystalline and electronic quality of GeOI substrates, unprecedented strain amplitudes were achieved in 350 nm thick Ge layers: 1.9 % (8.1 cm
^-1
) for biaxial strain, 4.9 % (9.9 cm
^-1
) for uniaxial stress along <;100> and 3.8 % (14 cm
^-1
) for uniaxial stress along <;110>. Two types of nonlinear strain dependences have been theoretically and experimentally demonstrated for uniaxial stress: the Raman-strain and the gamma bandgap-strain relations. We will discuss the consequences of the updated relationships to obtain the building blocks needed to fabricate an efficient laser based on highly strained Ge material.