As groundbreaking light emitters in the visible and UV range, GaN vertical cavity surface emitting lasers (VCSELs) have the potential to disrupt incredibly lucrative markets, but they currently face obstacles that limit their large-scale adoption against alternative products. Long cavity GaN VCSEL designs show much promise due to their improved thermal performance and reduced processing constraints, and Long cavity designs coupled with the use of epitaxial DBRs push the performance even further, but there still remains the obstacle of the poor electrical conductivity of p-GaN layers. Tunnel junctions (TJs) have been employed to overcome this obstacle, but their high turn-on voltage and stringent optical confinement requirements pose another barrier. Overcoming this barrier would usher in a new generation of light emitters with wide applications from displays to visible light communication (VLC).
Researchers at the University of California, Santa Barbara have implemented a planar tunnel junction (TJ) in a III-Nitride-based vertical cavity surface emitting laser (VCSEL) that circumvents the typical TJ drawbacks and further improves device performance. This technology demonstrates reduced optical loss within the cavity as well as reduced turn-on voltage through sidewall treatment and activation. An ion implantation current aperture TJ replaces the conventional buried TJ, allowing for enhanced activation of the p-type GaN and, in turn, reduced turn-on voltage, increased gain, and improved efficiency. The invention also resolves the performance-hindering effects of sidewall damage by implementing a phosphoric acid dip, ultraviolet-ozone treatment, and buffered hydrofluoric acid dip to remove the damaged sidewall and improve activation. This further reduces the turn-on voltage and results in higher wall-plug efficiency.