Ge—si p-i-n photodiode with reduced dark current and fabrication method thereof

Abstract

Various embodiments of a germanium-on-silicon (Ge—Si) photodiode are provided along with the fabrication method thereof. In one aspect, a Ge—Si photodiode includes a doped bottom region at the bottom of a germanium layer, formed by thermal diffusion of donors implanted into a silicon layer. The Ge—Si photodiode further includes a doped sidewall region of Ge mesa formed by ion implantation. Thus, the electric field is distributed in the intrinsic region of the Ge—Si photodiode where there is low dislocation density. The doped bottom region and sidewall region of the Ge layer prevent electric field from penetrating into the Ge—Si interface and Ge mesa sidewall region, where a large amount of dislocations are distributed. This design significantly suppresses dark current.