Ge 0.9 Sn 0.1 multiple-quantum-well p-i-n photodiodes for optical communications at 2 μm

We demonstrate a Ge 0.9 Sn 0.1 multiple-quantum-well p-i-n photodiode on Si substrate with a cutoff wavelength beyond 2 μm. A record-low dark current density of 31 mA/cm 2 at V bias = −1V is achieved.