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


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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 (VZn-R) defects with dopants in degenerately Ga-doped ZnO grown by pulsed laser deposition. DRCLS VZn-R/conduction band emission ratios relate to acceptor/donor concentrations, increasing rapidly for growth temperatures >400 °C, evidently because Ga atoms are inhibited from incorporating efficiently on available VZn 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 VZn-R densities on a nm scale, confirming the acceptor nature of VZn-R defects.