Planar laterally oxidized VCSELs for high density laser arrays

We present results on an improved fabrication strategy for VCSELs utilizing lateral oxidation. Laterally oxidized (LO) VCSELs are typically fabricated by etching a mesa and oxidizing inwards from the sides of the mesa to define the laser aperture. Due to the requirement that the etch must penetrate through the upper mirror of the VCSEL structure to a buried oxidation layer, the mesa step height is typically large, resulting in difficulties in making electrical contact to the resulting devices. Typically either mesas are fabricated large enough to accommodate an electrical contact, resulting in very large spacings between laser elements, or some planarization process, such as polyimide, is adopted in order to provide a surface suitable for electrical contact to a smaller mesa. If the top VCSEL mirror is a dielectric mirror, mesa heights are reduced and contacting is facilitated, however, fabrication of both mirrors epitaxially results in a much more robust process. The planar lateral oxidation (PLO) process that we demonstrate here utilizes fully epitaxially grown VCSEL structures with no dielectric mirrors, yet eliminates the constraints associated with the typical mesa etch for oxide device definition.