Role of native point defects and Ga diffusion on electrical properties of degenerate Ga-doped ZnO

We used a complement of depth-resolved cathodoluminescence spectroscopy (DRCLS), X-ray photoemission spectroscopy (XPS), and Hall-effect measurements to demonstrate the interplay of Zn vacancy-related (V-Zn-R) defects with dopants in degenerately Ga-doped ZnO grown by pulsed laser deposition. DRCLS V-Zn-R/conduction band emission ratios relate to acceptor/donor concentrations, increasing rapidly for growth temperatures >400 degrees C, evidently because Ga atoms are inhibited from incorporating efficiently on available V-Zn sites. Elemental XPS depth profiles reveal a temperature-dependent Ga interface segregation due to Ga bulk diffusion during growth. DRCLS Fermi level thresholds provide a useful indicator of carrier density, revealing depth variations in carrier density that anticorrelate with V-Zn-R densities on a nm scale, confirming the acceptor nature of V-Zn-R defects. (C) 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim