Silicon–on–insulator waveguide photodetector with Ge/Si self-assembled islands

We have investigated a silicon-based near-infrared photodetector using a waveguide with strong optical confinement. The high-difference index waveguide is obtained with a silicon–on–insulator substrate. The optically active region consists of self-assembled Ge/Si islands embedded in a $\mathrm{p-i-n}$ junction. The Ge/Si islands grown by high-pressure chemical-vapor deposition exhibit a broad photoluminescence and electroluminescence which are resonant around 1.5 μm. The photoluminescence and electroluminescence energies are correlated to the island size and to the island composition using a six-band k⋅p calculation. The spectral responsivity of the detectors is measured in a front facet coupling geometry with a broadband source and with semiconductor laser diodes. For a 0 V applied bias, responsivities of 25 and 0.25 mA/W are measured at room temperature at 1.3 and 1.55 μm, respectively.