30 GHz GeSn photodetector on SOI substrate for 2 µm wavelength application

We report the demonstration of a normal-incidence p-i-n germanium-tin ( Ge 0.951 Sn 0.049 ) photodetector on silicon-on-insulator substrate for 2 μm wavelength application. The DC and RF characteristics of the devices have been characterized. A dark current density under − 1 V bias of approximately 125 mA/ cm 2 is achieved at room temperature, and the optical responsivity of 14 mA/W is realized for illumination wavelength of 2 μm under − 1 V reverse bias. In addition, a 3 dB bandwidth ( f 3 dB ) of around 30 GHz is achieved at − 3 V , which is the highest reported value among all group III–V and group IV photodetectors working in the 2 μm wavelength range. This work illustrates that a GeSn photodetector has great prospects in 2 μm wavelength optical communication.