40 Gb/s surface-illuminated Ge-on-Si photodetectors

This paper reports on surface illuminated Ge photodetectors monolithically integrated on Si substrate operating in the C and L wavelength bands. The responsivity at a wavelength of 1.5 μm ranges from 0.08 to 0.21 A/W without bias voltage for Ge mesa diameter ranging from 10 to 25 μm, respectively. The measured −3 dB cut-off frequency is as high as 49 GHz under a reverse bias of 5 V at a wavelength of 1.5 μm. An open eye diagram up to 40 Gbit/s is also demonstrated.