Monolithic Waveguide-Integrated Group IV Multiple-Quantum-Well Photodetectors on 300 mm Si Substrates

We report a monolithic waveguide integrated Ge_0.92Sn_0.08/Ge multiple-quantum-well (MQW) photodetector (PD) on the 300-mm Si wafer for $2 \mu \text{m}$ wavelength detection and optoelectronic integrated circuits. We take advantage of the Ge layer serving as a buffer layer between the GeSn absorption layer and the Si substrate to realize the Ge-on-Si grating coupler and the waveguide for optical coupling and transmission so that the light can be evanescently coupled to the top GeSn absorption layer from the waveguide directly and enhance the responsivity. Our waveguide PD exhibits one of the lowest dark current densities of $3.6\times10$ ⁻² A/cm² among GeSn PDs and a high $2 \mu \text{m}$ responsivity of 47.4 mA/W, offering three times enhancement in responsivity as compared with the surface illuminated mode using the same absorption structure. These promising results, together with the removal of using more expensive silicon-on-insulator (SOI) wafer, demonstrate the potential of our approach to offer a cost-effective, large-scale manufacturable, and complementary-metal-oxide-semiconductor (CMOS) compatible solution to realize high performance, compact, and robust optoelectronic integrated systems at $2 \mu \text{m}$ wavelength which could enable enormous emerging applications, such as data communication, infrared sensing and imaging.