Systems, methods, and devices for reducing optical and electrical crosstalk in photodiodes

An avalanche photodiode, comprising:

• a first layer comprising passive material;
• a second layer comprising an absorbing material, the second layer on the first layer;
• a third layer on the second layer;
• an active region comprising a buried p-n junction and having an electric field greater than zero, the active region comprising at least a first portion of the second layer and at least a first portion of the third layer;
• and
• a plateau structure based on a first absence of a second portion of the second layer and a second absence of a second portion of the third layer.

A method for forming a photodiode, comprising:

• forming a first layer comprising passive material;
• forming a second layer comprising an absorbing material, the second layer on the first layer;
• forming a diffused region comprising a buried p-n junction;
• forming an active region comprising the buried p-n junction and having an electric field greater than zero;
• and
• forming a plateau structure based on removal of a portion of the second layer to the first layer to form a trench in the second layer extending downward to the first layer.