Near infrared light detectors based on UHV-CVD epitaxial Ge on Si (100)

In the present work we investigate photo-detectors based on thick relaxed Ge layers, epitaxially grown on silicon after insertion of a low-temperature-grown Ge buffer layer. By using this procedure it was possible to grow films having thicknesses comparable with light penetration depth in the 1.3-1.6 μm spectral range. The films exhibited flatness on the atomic scale. Two kinds of detectors were investigated: vertical heterojunction diodes and a planar Metal-Semiconductor-Metal structure. The detectors show a good responsivity at normal incidence at both 1.3 and 1.55 μm. The photocurrent increases with the voltage applied, reaching a maximum responsivity of 0.24 A/W at 1.3 μm under a bias of 1 V. A complete optoelectronic characterization of the fabricated devices is performed. The results confirm the feasibility of the proposed approach for the fabrication of 1.3-1.55 μm near infrared photodetectors integrated on silicon chips.