Monolithic Waveguide Group IV Multiple-Quantum-Well Photodetectors and Modulators on 300-mm Si Substrates for 2-μm Wavelength Optoelectronic Integrated Circuit

We report a monolithic integration platform that integrates the grating coupler, waveguide, waveguide-coupled photodetectors (PDs), and waveguide-coupled electroabsorption modulators (EAMs) on 300-mm Si substrates for 2-
$\mu \text{m}$
wavelength applications. Our waveguide PDs and EAMs employ Ge0.92Sn0.08/Ge multiple quantum wells (MQWs) as the active layer. The Ge-on-Si buffer layer is utilized for the waveguide and grating coupler so that the light can be coupled from the fiber to the EAM and PD for direct modulation and detection. For the PDs, the waveguide-coupled mode extends the absorption path and enables the realization of the highest responsivity of 525 mA/W among all the reported GeSn-based 2-
$\mu \text{m}$
PDs, which is 35 times higher than the surface illuminated PD with the same active layer. A 3-dB bandwidth is measured to be 6 GHz at −7 V. For the EAM, at a 2004-nm wavelength, the extinction ratio is 2.02 dB with −10.9-dB insert loss.