Managing Detection Region Spacing in an Integrated Photodetector

A method for fabricating a photodetector on a silicon-on-insulator (SOI) substrate that includes at least one silicon dioxide layer and at least one silicon layer, with a first surface of the silicon layer adjacent to the silicon dioxide layer, the method comprising:

• forming at least one optical waveguide within at least a portion of the silicon layer, the optical waveguide defining an incident optical mode of an incident optical wave;
• forming at least one detection region configured to receive a detected optical mode that is coupled to the incident optical mode, the detection region consisting essentially of an intrinsic semiconductor material adjacent to a second surface of the silicon layer;
• forming a spacing structure surrounding at least a portion of the detection region, the spacing structure comprising a p-type doped semiconductor region adjacent to a first portion of the detection region and an n-type doped semiconductor region adjacent to a second portion of the detection region;
• depositing a dielectric layer over at least a portion of the spacing structure, with the silicon layer of the SOI substrate located between the dielectric layer and the silicon dioxide layer of the SOI substrate;
• forming a first metal contact structure within a trench in the dielectric layer electrically coupling to the p-type doped semiconductor region without contacting any of the intrinsic semiconductor material of the detection region;
• and
• forming a second metal contact structure within a trench in the dielectric layer electrically coupling to the n-type doped semiconductor region without contacting any of the intrinsic semiconductor material of the detection region.