36-GHz High-Responsivity Ge Photodetectors Grown by RPCVD

We present high-speed Ge p-i-n photodetectors for vertical incidence with high responsivity, grown by reduced pressure chemical vapor deposition. From the high-resolution X-ray diffraction analysis, the Ge epilayer shows good crystalline homogeneity and the residual tensile strain of 0.16%. The fabricated device exhibits the 3-dB bandwidth of 36 GHz, the responsivity of 0.47 A/W, and low dark current of 42 nA at $\lambda \sim 1.55\ \mu$m. The same device also shows the responsivity of 0.7 A/W at $\lambda \sim 1.31\ \mu$m. The on-chip measurement of the eye diagram shows a good opening at 40-Gb/s data transmission.