Enhanced photocurrent and persistent photoconductivity in nanoporous GaN formed by electrochemical etching

The photoluminescence and spectral photoconductivity of nanoporous GaN (NP-GaN) produced by electrochemical etching have been investigated. The NP-GaN showed large yellow luminescence attributed to the radiative recombination through surface states. It also displayed higher photocurrent and larger persistent photoconductivity compared to unetched n-GaN. Careful measurement of the below-band-edge photocurrent revealed an energy barrier of 304 meV for the recombination of photogenerated electrons and holes. This peculiar photoresponse could be explained with a space charge model in the nanoporous structure. The nanoporous GaN could be applied to the design of efficient solar cells and solar fuel devices. - Highlights: • Optical properties of nanoporous GaN were characterized. • Enhanced photocurrent in nanoporous GaN was attributed to the charge separation. • Persistent photoconductivity was observed in the nanoporous GaN. • Significant below-band-edge photocurrent was monitored from 475 to 900 nm. • Energy barrier for photogenerated electrons was ∼ 304 meV