Porosity-induced relaxation of strains at different depth of nanoporous GaN studied using the Z-scan of Raman spectroscopy

• Nanoporous GaN with propagation and/or widening of nanopores was fabricated.
• Porosity within the etched layer increases with increasing etching depth.
• Porosity can be evaluated by the Z scan of Raman spectroscopy.

Propagation and/or widening of nanopores within the etched layers were usually observed by cross-sectional scanning electron morphology which is a destructive method for etched samples. In this study, nanoporous GaN with propagation and/or widening of nanopores fabricated using a UV-assisted electrochemistry etching procedure was studied using the Z scan of Raman spectroscopy. Comparison of nanoporous GaN with as-grown GaN showed that the strain relaxation and elastic modulus increases and decreases with increasing porosity within the etched layer, respectively. This work provides a new method for nondestructive and qualitative study on the porosity change within the etched layers of porous films.

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