Epitaxial SiGeC photodiode grown on Si substrate with response in the 1.3- to 1.55-μm wavelength range

We present results on epitaxial SiGeC alloy layers grown on Si substrates for optical receiver applications in the 1.3 - 1.55 μm wavelength range. The active absorbing layer of the pin photodiodes consist of a strained SiGeC alloy. The SiGeC alloy has a Ge content of 55% and 40%, with a thickness of 80 nm and 200 nm, respectively. TEM images review a high quality epitaxial film with a sharp interface between the SiGeC layer and the Si substrate. The devices show a breakdown voltage of about 6 V. Both surface normal and waveguide structures have been fabricated, and optical response extending to 1.55 μm has been demonstrated. At normal incidence the external quantum efficiency of the device with a 55%-Ge content is close to 1% at 1.3 μm. For a waveguide structure of 400-micrometers length the external quantum efficiency is 8% at 1.3 μm, and limited by the fiber coupling coefficient.