Metal–Ge-Si heterostructures for near-infrared light detection

We report on Ge Schottky photodiodes epitaxially grown on Si (100) exhibiting a good responsivity in the near infrared up to 1.55 μm. The Ge epitaxial layers, grown by ultrahigh vacuum chemical vapor deposition, were deposited in two steps differing by the substrate temperature. With this procedure it was possible to obtain films thicknesses comparable with light penetration depth in the 1.3–1.6 μm range. The photodiodes have a photocurrent which increases as a function of voltage bias, reaching a maximum responsivity of 0.12 A/W at 1.3 μm under a reverse bias of 4 V. The leakage current density at the saturation voltage is 1 nA/μm2. The results show that the proposed approach is promising for the fabrication of 1.3–1.55 μm near-infrared photodetectors integrated on silicon chips.