Photogalvanic Etching of n-GaN for Three-Dimensional Electronics
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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 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
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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.
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