Contact Architectures for Tunnel Junction Devices

A commonly explored limitation of p-GaN is that it is a poor current spreading layer and that traditional p-contacts will increase operating voltages in III-nitride devices. The introduction of tunnel junctions solves these issues and expands the opportunities for new device designs. This technology seizes the opportunity to improve the light extraction of flip chip LEDs.

Researchers at the University of California, Santa Barbara have optimized light extraction of tunnel junction devices by increasing the reflectivity of the device’s mirror. The high reflectivity of silver has made it the first choice for previous mirror iterations, but its poor conductivity at the requisite thinness requires adjustments which then erode the benefits of its high reflectivity. This technology reconstructs the mirror, replacing silver with aluminum and coating the reflector with a dielectric high-reflection coating. This novel mirror architecture demonstrates a higher reflectivity than pure silver which leads to improved light extraction.