Ge—Si P-I-N photodiode with reduced dark current and fabrication method thereof

摘要

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.

主权项

1. A photodiode comprising:
a substrate layer; a bottom contact layer of a first semiconductor material and disposed on the substrate layer, the bottom contact layer doped to exhibit a first conductive type; an absorption layer of a second semiconductor material and disposed on the bottom contact layer, the absorption layer comprising:
a bottom doped region doped to exhibit the first conductive type, wherein a doping profile of the bottom doped region is gradually doped with higher concentration at an interface between the bottom contact layer and the absorption layer, and with lower concentration away from the interface between the bottom contact layer and the absorption layer;an ion-implanted sidewall region doped to exhibit the first conductive type; andan intrinsic region unintentionally doped or lightly doped to function as a depletion region; a top contact layer doped to exhibit a second conductive type and disposed on the absorption layer; and an anti-reflection layer disposed on the top contact layer.