Development of Fabrication Techniques for High Extraction Efficiency Bulk-GaN-Based LEDs

While there have been tremendous advances in light-emitting diode (LED) technology based on gallium nitride (GaN), LED performance still falls short of what is required for solid-state lighting to become a ubiquitous general illumination solution. Recently, it has been demonstrated that considerable improvements in internal quantum efficiency can be realized on novel nonpolar and semipolar orientations of GaN, using high-quality bulk-GaN substrates. However, techniques for achieving high-extraction efficiency out of packaged devices on bulk-GaN substrates have not yet been developed, and novel manufacturing techniques are required. This project will develop a manufacturing process for the implementation of high-extraction-geometry devices on bulk-GaN substrates, leading to the next-generation of high brightness LEDs. Phase I will focus on the development and application of bandgap-selective photoelectrochemical (PEC) etching for controlled GaN substrate thinning, specifically in nonpolar and semipolar orientations. In Phase II, the manufacturing-friendly process will be optimized for high-extraction devices, and fully packaged devices will be fabricated and used to measure the enhancement in extraction efficiency. Commercial Applications and other Benefits as described by the awardee:The technology should accelerate the commercialization of next-generation LED devices by providing products with external quantum efficiencies (EQEs) that far exceed the current state-of-the-art. The availability of such LED products would enable the production of novel LED-based solid state white light sources with luminous efficiencies exceeding 150 lm/W, which would be representative of viable replacements for traditional incandescent and fluorescent lighting