We have etched GaN grown by plasma source MBE in aqueous solutions of KOH in an electrochemical cell under HeCd laser illumination and additional current control.The etch rate was dramatically enhanced up to 8 μm/h by an applied current density of 6.4 mAcm−2. Photocurrent control leads to etched GaN surfaces exhibiting mirror-like appearance with uniform interference color. According to mechanical profilometry, they have a roughness of less than 3.5 nm after etching of several hundred nanometers, which is comparable to the roughness prior to etching. This etching process allows in situ control via photocurrent and induced yellow luminescence.
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The authors wish to thank Dr. D. Lipinsky for helpful discussions and A. Pohl for SEM photos. The research was supported by Dr. N. Roy, Bonn, and H.-P. Werno, Koblenz.
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Rotter, T., Uffmann, D., Ackermann, J. et al. Current Controlled Photoelectrochemical Etching of GaN Leaving Smooth Surfaces. MRS Online Proceedings Library 482, 998–1003 (1997). https://doi.org/10.1557/PROC-482-1003