(Invited) Applications of Electrochemistry for Novel Wide Bandgap GaN Devices

In the recent two decades we have witnessed phenomenal progress in GaN optoelectronic and power electronic devices, culminating in the recent 2014 Nobel Prize in Physics. In both light emitting devices and power transistors, GaN has transitioned from laboratory curiosity to commercial maturity. Most of the innovative claims nowadays need to be benchmarked with industrial manufacturability and cost effectiveness. We intend to show in this talk new opportunities rendered by applying electrochemistry to GaN. Recently our group discovered a simple and versatile electrochemical (EC) etching of GaN at room temperature with no need of any ultraviolet irradiation.[i] The EC etching relies on the generation of holes at the GaN/electrolyte surface for oxidation and chemical dissolution. Depending on the layer conductivity and applied bias, the EC etching may cause no effect, nanoscale porosification, or complete etching of GaN.[ii] The EC etching has been applied to different areas of GaN material and device technologies, including layer separation, LED light extraction, the formation of distributed Bragg reflector (DBR) for photonic applications, and the preparation of flexible GaN membrane devices. Highlights from each application will be reviewed in this talk. The work was supported by the U.S. Department of Energy, National Science Foundation (NSF), and Seoul Optodevices. [i] Zhang, Y. et al., “A conductivity-based selective etching for next generation GaN devices”, Physica Status Solidi B 2010 247, 1713-1716 [ii] Zhang, Y. et al., “The fabrication of large-area, free-standing GaN by a novel nanoteching process”, Nanotechnology 2011, 22, 045603