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

•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.

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.