First Demonstration of Monolithic Waveguide-Integrated Group IV Multiple-Quantum-Well Photodetectors on 300 mm Si Substrate for $2\ \mu \mathrm{m}$ Optoelectronic Integrated Circuits

We report the first demonstration of a monolithic waveguide integrated Ge
0.92
Sn
0.08
/Ge multiple-quantum-well (MQW) photodetector (PD) for
$2\ \mu \mathrm{m}$
wavelength detection on the 300 mm Si wafer. The first of such device for group IV materials. We take advantage of the Ge buffer between the high-quality GeSn absorption layer and Si substrate to realize the Ge-on-Si waveguide and grating coupler so that the light can be evanescently coupled to the top GeSn absorption layer from the waveguide directly with an extended coupling path for enhanced responsivity. Our waveguide PD exhibits one of the lowest dark current densities of
$3.6\times 10^{-2}$
A/cm
²
among GeSn PDs and a high
$2\ \mu \mathrm{m}$
responsivity of 47.4 mA/W, offering 3 times enhancement in responsivity as compared with surface illuminated mode with the same absorption structure. These promising results, together with the removal of using more expensive SOI wafer, our approach offers a cost-effective, large-scale manufacturable, and CMOS compatible solution to realize high performance, compact, and robust optoelectronic integrated systems at
$2\ \mu \mathrm{m}$
wavelength which could enable enormous emerging applications, such as data communication and infrared sensing and imaging.