A method of forming an array of photodiodes includes forming a cap layer on a surface of an absorption layer. The method includes forming a plurality of spaced apart pixel diffusion areas in the cap layer. The method includes 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. The method includes 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.