Near-infrared metal–semiconductor–metal photodetector integrated on silicon

Abstract

We report on a metal–semiconductor–metal photodetector for the near infrared based on a thick relaxed Ge layer grown on a silicon substrate. The device exhibits a photoresponse spectrum extending down to 1.55 μm with maximum responsivity of 150 mA/W at the wavelength of 1.3 μm. An interdigited geometry allows a photoresponse speed of approximately 1.6 ns at low (1.5 V) bias voltage. Ge films were grown by solid source molecular beam epitaxy and characterised in situ with low energy electron diffraction and Auger spectroscopy. The crystalline quality was investigated by transmission electron microscopy and X-ray diffraction, while atomic force microscopy was used to assess surface morphology.