Photoluminescence related to Gd 3+ :N-vacancy complex in GaN:Gd multi-quantum wells

•We grew Gd-doped GaN multi-quantum wells (MQWs) with quantum layer thickness of one nm by MBE.•The X-ray absorption near edge structure spectra observed at Gd LIII-edge indicate a nitrogen vacancy adjacent to Gd substituting the Ga ion in Gd-doped GaN MQW.•The photoluminescence of the samples is discussed considering the formation of a Gd3+:Nitrogen-vacancy complex.•A model is presented considering exciton-polaron formation trapped in defect sites around the Gd3+:N-vacancy complex in Gd-doped GaN MQWs.