Light detection with semiconductor photodiodes

A semiconductor photodiode comprising:

• a top side with an active surface area for light entry into the photodiode;
• a bottom side opposite to the top side;
• a bulk structure comprising a single semiconductor material, the bulk structure comprising:
• a p+-type layer and an n-type layer, which together form the p-n junction of the photodiode, wherein one of the two layers of the p-n junction is an upper p-n junction layer and the other one is a lower p-n junction layer, wherein the upper p-n junction layer is located proximate to the active surface area;
• an n-type enrichment layer and a p-type guard ring, wherein the guard ring runs along the circumference of the p+-type layer and is embedded in the n-type layer, and wherein the n-type enrichment layer is located below the p+-type layer, in direct surface contact with the p+-type layer and embedded in the n-type layer;
• and
• a semiconductor light absorption layer;
• wherein:
• the semiconductor light absorption layer defines the active surface area;
• the semiconductor light absorption layer is arranged on top of the bulk structure, above the upper p-n junction layer;
• the semiconductor light absorption layer comprises a different semiconductor material from the semiconductor material of the bulk structure;
• and
• a precursor layer is arranged between the bulk structure and the semiconductor light absorption layer, wherein the semiconductor light absorption layer is in direct contact with on the precursor layer.