Electrical and optical properties of ZnO bulk crystals with and without lithium grown by the hydrothermal technique

Buguo Wang; Bruce Claflin; Michael Callahan; Z. -Q. Fang; David Look

doi:10.1117/12.2042344

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8 March 2014 Electrical and optical properties of ZnO bulk crystals with and without lithium grown by the hydrothermal technique

Buguo Wang, Bruce Claflin, Michael Callahan, Z. -Q. Fang, David Look

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Proceedings Volume 8987, Oxide-based Materials and Devices V; 89871D (2014) https://doi.org/10.1117/12.2042344
Event: SPIE OPTO, 2014, San Francisco, California, United States

Abstract

Lithium is usually added into the solution to improve ZnO hydrothermal growth; however, lithium doping affects the properties of the resulting crystals. Optical and electrical properties of hydrothermal ZnO bulk crystals without lithium, have been studied by photoluminescence and Hall-effect measurements. High quality ZnO crystals without lithium were grown in H₂O/D₂O and in NH₃-H₂O solutions. The crystals grown from H₂O/D₂O are conductive with resistivities of 0.6-0.7 Ωcm and mobilities of ~ 100 cm²/Vs, while lithium doped ZnO crystals typically have resistivities of ~ 10³Ω-cm and mobilities of ~ 200 cm²/Vs, but can be varied from dozens to 10¹⁰ Ω-cm depending on lithium concentration. Lithium-free but nitrogen doped crystals grown in NH₃-H₂O solution have resistivities of 1×10⁰ Ω-cm and sometimes show p-type conduction; the resistivity increases to ~ 1×108 Ω-cm after annealing at 600° C in air. Lithium and nitrogen co-doped ZnO crystals have resistivities of 10⁸-1012 Ω-cm and are semi-insulating after annealling. Electronic irradiation also increases the ZnO resistivity. For lithium-doped samples, a 3.357 eV peak can be seen in the photoluminescence spectra. This is close to the donor-exciton peaks in indium-doped ZnO where 3.3586 eV and 3.357 eV were found on the C⁺ and C^- faces, respectively. More studies are needed to identify lithium-related complexes (defects).

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Buguo Wang, Bruce Claflin, Michael Callahan, Z. -Q. Fang, and David Look "Electrical and optical properties of ZnO bulk crystals with and without lithium grown by the hydrothermal technique", Proc. SPIE 8987, Oxide-based Materials and Devices V, 89871D (8 March 2014); https://doi.org/10.1117/12.2042344

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