Growth and characterization of tree-like crystalline structures during electrochemical formation of porous GaN

Abstract

Electrochemical etching of crystalline n-GaN in H2SO4:H2O2 results in the formation of porous GaN. Scanning electron microscopy images revealed the presence of branches on the surface of porous GaN and showed the varying stages with etching time. The branches on the surface of the porous GaN that have been associated with Ga2O3 have a significant enhancing effect on the photoluminescence intensity. Raman spectra of both as-grown and porous GaN exhibit phonon mode E2 (high), A1 (LO), A1 (TO) and E2 (low). There is a red shift in E2 (high), indicating a relaxation of compressive stress in the porous GaN surface with respect to the underlying single-crystalline epitaxial GaN.