Development of highly reflective mirrors for III-nitrides from green to UV

Abstract

GaN-based vertical-cavity surface emitting lasers (VCSELs) have attracted significant attention in recent years for their potential applications in solid-state lighting, optical communications, laser printing, and display technologies. The main challenge in the development and commercialization of GaN-based VCSELs is the absence of electrically conductive epitaxial distributed Bragg reflectors (DBRs) with high crystal quality and near-unity reflection. The GaN VCSELs based on the epitaxial (AlGaN/GaN or AlInN/GaN) DBRs and dielectric DBRs have been actively studied and demonstrated by several research groups. Besides, the blue VCSELs using the lattice-matched and electrically conductive nanoporous (NP) GaN DBR, composed of GaN/NP GaN alternating layers fabricated in a manufacturable way, have been recently demonstrated by our group and University of New Mexico. We will discuss these DBR mirror technologies as well as the nano-engineering based on the electrochemistry to create NP (Al)GaN as a low index medium. The selective nanopore formation/fabrication, mainly depending on the electrical conductivity contrast between the alternating layers, can be carried out on a large scale and barely necessitates complex growth techniques and structural limitations, resulting in manufacturable DBR fabrication for III-nitrides from green to UV.