Excimer Laser Lift-off for Packaging and Integration of GaN-based Light-emitting Devices

摘要

The delamination of a thin film heterostructure by selective absorption of pulsed laser energy at a buried interface enables the transfer of the thin film heterostructure from its growth substrate to virtually any receptor substrate without significant heating of material outside the interaction zone. By combining this "laser lift-off process with low-temperature bonding methods, disparate classes of materials can be intimately integrated without exceeding the thermal budget of the least robust of the materials to be integrated. Furthermore, heterostructures that can be grown by epitaxy on one substrate can be transferred intact, without significant deterioration in crystal quality, to a receptor substrate that enhances the performance or functionality of the heterostructure in a device or microsystem. In this paper, applications of laser lift-off in the packaging and integration of light-emitting GaN devices are highlighted. Transfer of these devices from their sapphire growth substrates to thermally and electrically conductive receptor substrates is shown to result in improved device performance through the reduction of thermal and electrical series resistances, and by the improvement in optical design enabled by access to both sides of the heterostructure. Continued development of laser lift-off packaging has the potential to reduce manufacturing costs and complexity as well through the elimination of the sapphire dicing step. Finally, the application of the LLO technique to the assembly of functionally-enhanced microsystems is illustrated with the example of an integrated fluorescence detection microsystem.