18 March 2013 Dopant profiles in heavily doped ZnO
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Proceedings Volume 8626, Oxide-based Materials and Devices IV; 862606 (2013) https://doi.org/10.1117/12.2009394
Event: SPIE OPTO, 2013, San Francisco, California, United States
X-ray photoelectron spectroscopy (XPS) is used to compare the composition as a function of depth of as-grown ZnO films heavily doped with Ga and similar samples annealed in air for 10 min. at 600 °C, with particular attention given to the near-surface region. These films were grown by pulsed laser deposition (PLD) using a ZnO target containing 3 wt% Ga2O3. The electrical properties of these samples were determined from temperature-dependent Hall-effect measurements. The as-grown film has the following characteristics: i) a ~1:1 Zn:O ratio with a Ga concentration of ~ 3.3 atomic percent; ii) no excess Ga in the near-surface region; and iii) excellent electrical characteristics: ρ=2.42×10-4 Ω-cm, n=8.05×1020 cm-3, and μ=32.1 cm2/V-s at 300 K. For the annealed sample: i) the Zn:O ratio remains ~ 1:1, but the Ga concentration is ~ 3 atomic percent which is ~10% lower than in the as-grown film; ii) ~7 at% Ga is measured in the near-surface region; and iii) a significant increase in resistivity to ρ = 0.99 Ω-cm, n = 1.97×1018 cm-3, and μ=3.2 cm2/V-s at 300 K. Analysis of the O chemical shift suggests formation of a mixed ZnO/Ga2O3 surface layer ≤ 5 nm thick accounts for the observed changes in the Ga profile after annealing.
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B. Claflin, B. Claflin, K. D. Leedy, K. D. Leedy, D. C. Look, D. C. Look, } "Dopant profiles in heavily doped ZnO", Proc. SPIE 8626, Oxide-based Materials and Devices IV, 862606 (18 March 2013); doi: 10.1117/12.2009394; https://doi.org/10.1117/12.2009394

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