Photodetectors and methods of formation

A method, comprising:

• etching a substrate to form a first recess in the substrate;
• depositing material of a shallow trench isolation (STI) region in the first recess;
• forming, in the substrate and laterally adjacent to a first side of the STI region, a first contact region of a photodetector device;
• etching the substrate to form a second recess in the substrate,
• wherein the second recess is laterally adjacent to a second side of the STI region opposing the first side;
• depositing, in the second recess, semiconductor material of a sensing region of the photodetector device,
• wherein the semiconductor material of the sensing region is different from a semiconductor material of the substrate;
• and
• depositing, on the sensing region, semiconductor material of a second contact region of the photodetector device,
• wherein the semiconductor material of the second contact region and the semiconductor material of the sensing region is a same semiconductor material.

A method, comprising:

• forming a first shallow trench isolation (STI) region and a second STI region in a substrate;
• depositing material of a top oxide layer over the substrate;
• forming, laterally adjacent to a first side of the first STI region, a first contact region of a photodetector device;
• etching the top oxide layer and the substrate to form a recess through the top oxide layer and into the substrate,
• wherein the recess is laterally adjacent to a second side of the STI region opposing the first side, and
• wherein the recess is laterally between the first STI region and the second STI region;
• depositing, in the recess, germanium material of a sensing region of the photodetector device,
• wherein the first contact region comprises a semiconductor material that is different than the germanium material of the sensing region;
• and
• depositing, on the sensing region, semiconductor material of a second contact region of the photodetector device,
• wherein the semiconductor material of the second contact region and the semiconductor material of the first contact region are different semiconductor materials.