Method for fabricating a photodiode structure and photodiode structure

Photodiode structure comprising a junction designed to transform an infrared electromagnetic radiation into electron-hole pairs, the junction comprising a first layer made from HgCdTe or one of its at least quaternary derivatives of a first conductivity type and a second layer made from HgCdTe or one of its at least quaternary derivatives of a second conductivity type opposite from the first conductivity type to form a p-n or p-i-n junction;

• wherein the first layer comprises:
• first and second ends, the first end being separated from the second layer by the second end;
• a first cadmium concentration gradient that is decreasing from the first end of the first layer in the direction of the second layer, a minimum value of the atomic cadmium concentration in the first cadmium concentration gradient being comprised between 10% and 25% atomic, the first cadmium concentration gradient defining a first portion and a second portion, the second portion having a smaller band gap width than the first portion;
• a second concentration gradient of at least one electrical dopant, the second concentration gradient being decreasing from the first end in the direction of the second layer;
• wherein the total thickness of the first layer and of the junction layer is less than 6 microns;
• wherein the first cadmium concentration gradient is continuously decreasing in the form of a diffusion profile,
• wherein the second concentration gradient of at least one electrical dopant is continuously decreasing in the form of a diffusion profile,
• wherein the second concentration gradient extends over a distance comprised between 500 nm and 1.5 microns from the first end, in the first layer,
• wherein the second concentration gradient is decreasing from a concentration of more than 5*1018 at/cm3 to a concentration of less than 2*1015 at/cm3;
• wherein the first cadmium concentration gradient extends until the first electrical dopant concentration is less than 2*1015 at/cm3
• and wherein first layer presents a larger thickness than the second layer.