GaN nanopyramid arrays were fabricated by a convenient electrode-less photo-electrochemical etching method. Transmission electron microscopy measurement indicated that these nanopyramids were composed of crystalline GaN surrounding a dislocation. High-resolution X-ray diffraction and the micro-Raman spectrum revealed a highly compressive stress relaxation in the nanopyramids compared with compressed GaN sub-film. Additionally, negative piezoelectric current pluses were generated from the GaN nanopyramids when the conductive atomic force microscope scans cross the arrays in the contact mode. The result demonstrated that the GaN nanopyramid arrays were a promising candidate for nanogenerators.

Structure, Stress State and Piezoelectric Property of GaN Nanopyramid Arrays. J.Liu, J.Wang, X.Gong, J.Huang, K.Xu, T.Zhou, H.Zhong, Y.Qiu, D.Cai, G.Ren, H.Yang: Applied Physics Express, 2011, 4[4], 045001