Indirect excitons in hydrogen-doped ZnO

We present a correlative experimental and theoretical study of bound excitons in hydrogen-doped ZnO, with a particular focus on the dynamics of their metastable state confined in the sub-surface region, using a combination of surface-sensitive characterisation techniques and density functional theory calculations. A metastable sub-surface emission at 3.31 eV found in H-doped ZnO is attributed to the radiative recombination of indirect excitons localised at basal plane stacking faults (BSFs) where the excitonic transition involves electrons bound to bond-centre hydrogen donors in the potential well of the BSF. Additionally, our work shows the electrical transport of ZnO Schottky junctions is dominated by electrons confined at BSFs in the near-surface region.