A Pathway to Fabricate Gallium Nitride Embedded 3D High‐Index‐Contrast Optical Structures

Abstract Optical engineering of gallium nitride (GaN) semiconductor material has enabled novel applications and technologies. 3D optical engineering is challenging and mostly accomplished by surface‐level patterning with subtractive or additive means. In this work a pathway, based on epitaxial conductivity control in conjunction with ion implant and subsequent electrochemical etching, to generate complex embedded nanoporous (NP)‐GaN/GaN or air/GaN 3D optical structures is presented. A range of subsurface structures is demonstrated including in‐plane NP‐GaN stripes and curved patterns, air/GaN microchannels, and localized, embedded distributed Bragg reflectors (DBRs) as micromirrors. To further demonstrate the versatility of the technique, adjacent DBR micromirrors, of different thicknesses, embedded depths, and widths, are created in the same fabrication steps. Computer simulations are used to shed light on the limitations of feature sizes of the presented technique. The approach is a simple, scalable, and versatile approach for fabricating embedded 3D optical structures readily extendable beyond GaN semiconductors.