The impact of nanoperforation on persistent photoconductivity and optical quenching effects in suspended GaN nanomembranes

Abstract

We report on fabrication of suspended ~15 nm thick GaN membranes nanoperforated in an ordered fashion using direct writing of negative charges by focused ion beam and subsequent photoelectrochemical etching of GaN epilayers. Both continuous and nanoperforated membranes exhibit persistent photoconductivity (PPC), which can be optically quenched under excitation by 546 nm radiation. Optical quenching of PPC occurs also under relatively intense intrinsic excitation of nanoperforated membranes by 355 nm radiation at T < 100 K. The proposed explanation is based on strong surface localization of charge carriers in nanoperforated membranes and UV-induced reactions occurring at surface states under intense intrinsic excitation.