A Nanoporous Route to Manufacture Next-Generation III-Nitride Devices and Substrates

Yale University, New Haven CT

Investigators

Abstract

This project exploits a recently discovered electrochemical process to create new manufacturing techniques for GaN that have not been possible. The project represents a bold integration of epitaxial optoelectronics with scientific interdisciplines including electrochemical processes, solid-phase mass transport, and applied fracture mechanics. At the same time the investigators seek to develop concrete, manufacturable processes that will impact the energy-efficient lighting and power distribution industries, projected to capture markets of hundreds of billion dollars by 2020. Three concrete objectives are (1) manufacture-friendly thin-film LEDs for general illumination, (2) the regenerative usage of heteroepitaxial substrates to offset the substrate cost in LED production, and (3) hybrid integration of GaN membrane devices with flexible hosts. The combination of a nanoscale porosification process with MOCVD epitaxy enables a flexible embedding of nano-voids and nano-cavity layer underneath LED device layers. The presence and coalescence of these nano-cavities facilitate wafer splitting, large-area layer transfer and, simultaneously, substrate recycling. Furthermore, the transferred, free-standing thin-film devices provide an ideal configuration as hybrid inorganic-organic flexible devices in both optoelectronics and electronics. The investigated etching-epitaxy-splitting process will open up untapped opportunities in substrate utilization, growth design, and device fabrication. GaN is a ubiquitous semiconductor that is finding applications in everyday life. This wide bandgap material is capable of producing efficient ultraviolet, blue, and green light for display and lighting. It is an ideal replacement for silicon as compact transistors for high-power electricity transmission and energy conversion. However, GaN is chemically inert and mechanically robust, thus imposing rigid constraints to fabrication techniques for mass production. In spite of the demonstrated superiority in optoelectronic and electronic performance, GaN LEDs and transistors still face a stiff bottleneck in the cost of manufacturing. This projects exploits a recently discovered electrochemical process to create new manufacturing techniques for GaN that have not been possible. It aims to propel the manufacture technology for solid state lighting into a smarter, greener, and more sustainable state based on nanoscale scientific insights. Using a simple anodization process to create a foam-like GaN, the investigators plan to demonstrate the possibility of micromachining GaN, including slicing and shaping thin layers, for manufacture-friendly and cost effectively fabrication of GaN devices for energy-efficient lighting and power distribution, an industry that is projected to capture markets of hundreds of billion dollars by 2020.