Mesa trench etch with stacked sidewall passivation

A method of forming an array of photodiodes comprising:

• forming a cap layer on a surface of an absorption layer;
• forming a plurality of spaced apart pixel diffusion areas in the cap layer, wherein each pixel diffusion area extends beyond the surface of the absorption layer and into the absorption layer to receive a charge generated from photons received through the absorption layer by the pixel diffusion area;
• forming a mesa trench with opposed sidewalls through the cap layer, wherein the mesa trench surrounds each of the pixel diffusion areas separating the pixel diffusion areas from one another;
• forming a sidewall passivation layer over the sidewalls of the mesa trench;
• and
• removing a portion of the sidewall passivation layer to expose a respective contact electrically connected to each of the pixel diffusion areas, but leaving the sidewalls of the mesa trench covered with the sidewall passivation layer wherein the contact is open and uncovered for electrical connection.