Low voltage avalanche photodiode with re-entrant mirror for silicon based photonic integrated circuits

摘要

A low voltage APD is disposed at an end of a waveguide extending laterally within a silicon device layer of a PIC chip. The APD is disposed over an inverted re-entrant mirror co-located at the end of the waveguide to couple light by internal reflection from the waveguide to an under side of the APD. In exemplary embodiments, a 45°-55° facet is formed in the silicon device layer by crystallographic etch. In embodiments, the APD includes a silicon multiplication layer, a germanium absorption layer over the multiplication layer, and a plurality of ohmic contacts disposed over the absorption layer. An overlying optically reflective metal film interconnects the plurality of ohmic contacts and returns light transmitted around the ohmic contacts to the absorption layer for greater detector responsivity.