GeSn photodetector spans all telecom wavebands
Germanium (Ge)-on-silicon photodetectors operate successfully in the telecommunications wavelength ranges centered at 1310 nm and 1550 nm (the C- and L-bands), respectively; however, the Ge direct bandgap of 0.8 eV severely limits its operation above 1550 nm, making these types of detectors not usable at L-band (1565 to 1625 nm) and U-band (1625 to 1675 nm) wavelengths.