Near-infrared waveguide photodetector with Ge/Si self-assembled quantum dots

We have investigated near-infrared $\mathrm{p-i-n}$ photodetectors with Ge/Si self-assembled quantum dots. The self-assembled quantum dots were grown by chemical vapor deposition on Si(001). A vertical stacking of 20 layers of quantum dots was inserted into a near-infrared waveguide obtained with a ${\mathrm{Si}}_{\text{0.98}}{\mathrm{Ge}}_{\text{0.02}}$ alloy. The samples were processed into ridge waveguides. The photoresponse of the device covers the near-infrared spectral range up to 1.5 μm. At room temperature, a responsivity of 210 mA/W is measured at 1.3 μm and 3 mA/W at 1.5 μm. The photocurrent is compared to the photoluminescence and to the absorption of the quantum dots measured in the waveguide geometry. At room temperature, the onset of the absorption is around 1.9 μm (0.65 eV). The photocurrent is blueshifted as compared to the absorption.