Ultra low dark current pin photodetector

A method for fabricating a photodetector, comprising:

• forming a substrate;
• forming a buffer layer on the substrate;
• forming an absorption layer on the buffer layer for receiving incident photons and generating charged carriers;
• forming an N-doped interface layer on the absorption layer, wherein the N-doped interface layer comprises an N-doped region in the absorption layer;
• forming a dielectric cap layer on the N-doped interface layer;
• forming a dielectric passivation layer above the dielectric cap layer;
• forming a p+ diffusion region within the dielectric cap layer, the N-doped interface layer and at least a portion of the absorption layer;
• and
• forming and coupling at least one contact on the p+ diffusion region.

A PIN photodetector, comprising:

• an N+ InP substrate;
• an N+ InP buffer layer formed on the N+ InP substrate;
• an intrinsic InGaAs absorption layer formed on the N+ InP buffer layer for receiving incident photons and generating charged carriers;
• an N-doped interface layer formed on the absorption layer, wherein the N-doped interface layer comprises a doped region of the absorption layer;
• a dielectric cap layer formed on the N-doped interface layer, wherein the N-doped interface layer reduces depletion width at an interface between the intrinsic InGaAs absorption layer and the dielectric cap layer;
• a dielectric passivation layer formed above the dielectric cap layer;
• a P+ Zn diffusion region formed within the dielectric cap layer, the N-doped interface layer and at least a portion of the absorption layer;
• and
• at least one metal contact formed on and coupled to the P+ Zn diffusion region.