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Large-area bow-free n plus GaN templates by HVPE for LEDs
Leach, J. H., Shishkin, Y., Udwary, K., Preble, E. A., & Evans, K. R. (2014). Large-area bow-free n plus GaN templates by HVPE for LEDs. In JI. Chyi, Y. Nanishi, H. Morkoc, J. Piprek, E. Yoon, & H. Fujioka (Eds.), GALLIUM NITRIDE MATERIALS AND DEVICES IX SPIE-INT SOC OPTICAL ENGINEERING. https://doi.org/10.1117/12.2041642
The economic and energy efficiency promise of solid state lighting drive a continuous need to reduce the cost and improve the efficiency of visible LEDs. Current III-N LED manufacturing is dominated by non-native substrate approaches which result in strained epitaxial films, high dislocation density in the buffer and device active regions, and large epiwafer bow, which together present major limitations in terms of LED device yield, performance, and cost. Large area sapphire substrates (6", 8", and beyond) are becoming available and present cost reduction potential yet they are even more vulnerable to strain and bow related issues. We present a novel approach to realizing a zero-bow relatively-thick GaN on sapphire template that can be made at essentially any diameter and which bodes well for improved device yield, performance, and cost. The elimination of bow is achieved through a simple cost-effective stress balancing technique involving backside deposition. The result is a large area GaN template which is flat at all temperatures and which has 10x lower dislocation density than current GaN buffers. We report on the properties of these templates and provide device data for LED structures grown thereon.
