Avalanche photodiode

A structure, comprising:

• a semiconductor substrate;
• a trench formed in the semiconductor substrate, the trench having sidewalls and a bottom;
• a semiconductor material having a first dopant type which lines the sidewalls and the bottom of the trench;
• an intrinsic photosensitive semiconductor material contacting the semiconductor material;
• a second semiconductor material having the first dopant type and which is in the trench and contacting the intrinsic photosensitive semiconductor material;
• and
• an isolation structure comprising reflective material surrounding the trench, and remotely positioned from the intrinsic photosensitive semiconductor material,
• wherein the intrinsic photosensitive semiconductor material comprises undoped Ge material and the second semiconductor material is a plug comprising sidewalls and a bottom surface that are in contact and surrounded by the intrinsic photosensitive semiconductor material, and outer sidewalls of the intrinsic photosensitive semiconductor material are devoid of the second semiconductor material.

A method comprising:

• forming a trench in a substrate;
• providing a liner of semiconductor material on sidewalls and a bottom of the trench;
• forming an undoped photosensitive material on the semiconductor material partially within the trench;
• forming a second semiconductor material on the undoped photosensitive material filling a remaining portion of the trench, wherein the second semiconductor material is formed partially on a top surface of the undoped photosensitive material on an outside of the trench;
• and
• forming trench structures with reflective oxide based material in the substrate adjacent to the liner of the semiconductor material and remote from the second semiconductor material
• wherein the undoped photosensitive material comprises undoped Ge material and the second semiconductor material is a plug comprising sidewalls and a bottom surface that are formed in contact and surrounded by the undoped photosensitive material, and outer sidewalls of the undoped photosensitive material are devoid of the second semiconductor material.