Charge state switching of Cu acceptors in ZnO nanorods

摘要

Undoped and Ga-doped ZnO nanorods both exhibit an intense green luminescence (GL) band centered at ~2.4eV. Unlike the defect-related GL in undoped nanorods, the GL band in Ga-doped nanorods displays a periodic fine structure separated by 72 meV, which consists of doublets with an energy spacing of 30 ± 3 meV. The emergence of the structured GL is due to the Cu~+ state being stabilized by the rise in the Fermi level above the 0/-(Cu~(2+)/Cu~+) charge transfer level as a result of Ga donor incorporation. From a combination of optical characterization and simulation using the Brownian oscillator model, the doublet fine structures are shown to originate from two hole transi-tions with the Cu~+ state located at 390 meV above the valence band.