Method for fabricating a self-focusing detector pixel and an array

Abstract

Disclosed is a method for fabricating an array of electromagnetic radiation responsive photodiodes, and an array fabricated in accordance with the method. The method includes steps of (a) providing a transparent substrate (12); (b) growing on the substrate an electrically conductive buffer layer (14), an n-type radiation absorbing layer (16), and a p-type cap layer (18) forming a p-n junction; and (c) etching first trenches through the cap layer, the radiation absorbing layer, and partially through the buffer layer for forming initial mesa structures each having a top surface, a base, and sloping sidewalls that terminate in the buffer layer. The method further (d) forms a passivating layer (22) on the sloping side walls; (e) forms an electrical contact (24) that surrounds the bases of the initial mesa structures and that makes an ohmic contact with a surrounding portion of the buffer layer; and (f) etches a plurality of second trenches through exposed portions of the buffer layer and into the substrate. The second trenches delineate a plurality of larger mesa structures each of which supports one of the initial mesa structures. A common layer of metalization (30) is applied to exposed surfaces of the second trenches and is coupled to each of the electrical contacts. Each of the larger mesa structures has sloping side walls disposed at an angle for supporting internal reflection of radiation that is incident on the substrate, thereby concentrating the incident radiation into the radiation absorbing layer.