Photogalvanic Etching of n-GaN for Three-Dimensional Electronics
Etching in wide-bandgap semiconductors such as GaN aids applications including transistors, sensors, and radioisotope batteries. Plasma-based etching can induce surface damage and contamination that is detrimental to device performance. We present a photoelectrochemical approach to etching n-type GaN (n-GaN) that is low-cost, simple, and environmentally benign compared to plasma approaches, with the potential for highly anisotropic etching that avoids material damage. n-GaN was etched in a dilute KOH solution with K2S2O8 oxidizer, ultraviolet (UV) irradiation, and a catalytic metal mask which served as both photomask and counter electrode. Relatively smooth, highly anisotropic, non-defect-selective etching was achieved at rates in excess of 200 nm/min when etching at 65°C. The obstacle of bath acidification was circumvented using the addition of buffering salts to the etchant bath, substantially extending the etchant bath lifetime and etching depth achievable in a single, uninterrupted etch. These results represent a major step toward a scalable, device-ready electrochemical etch for vertical GaN structures and devices.
KeywordsGallium nitride electrochemical etching wide-bandgap semiconductors semiconductor fabrication
Unable to display preview. Download preview PDF.
This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under contract no. DE-AC52-07NA27344, LLNL-JRNL-758918. The authors would like to thank the following sources of funding: Army Research Office (ARO-W911NF-14-4-0341) and the LLNL Livermore Graduate Scholar Program.
- 8.F. Medjdoub and K. Iniewski, Gallium Nitride (GaN): Physics, Devices and Technology (2016)Google Scholar
- 23.J.L. Weyher and J.J. Kelly, in Springer Handbook Crystal Growth (Springer, Berlin, Heidelberg, 2010), pp. 1453–1476.Google Scholar
- 26.N. Takeno, Atlas of Eh-PH Diagrams (National Institute of Advanced Industrial Science and Technology Research Center for Deep Geological Environments, 2005).Google Scholar