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

We report on Ge Schottky photodiodes epitaxially grown on Si (100) exhibiti ng a good responsivity in the near infrared up to 1.55 mu m. The Ge epitaxi al layers, grown by ultrahigh vacuum chemical vapor deposition, were deposi ted in two steps differing by the substrate temperature. With this procedur e it was possible to obtain films thicknesses comparable with light penetra tion depth in the 1.3-1.6 mu m range. The photodiodes have a photocurrent w hich increases as a function of voltage bias, reaching a maximum responsivi ty of 0.12 A/W at 1.3 mu m under a reverse bias of 4 V. The leakage current density at the saturation voltage is 1 nA/mu m(2). The results show that t he proposed approach is promising for the fabrication of 1.3-1.55 mu m near -infrared photodetectors integrated on silicon chips. (C) 1999 American Vac uum Society. [S0734-211X(99)07402-8].