18 March 2013 Model for thickness dependence of mobility and concentration in highly conductive ZnO
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Proceedings Volume 8626, Oxide-based Materials and Devices IV; 862602 (2013) https://doi.org/10.1117/12.2001287
Event: SPIE OPTO, 2013, San Francisco, California, United States
Abstract
The dependences of the 294-K and 10-K mobility μ and volume carrier concentration n on thickness (d = 25 – 147 nm) were examined in Al-doped ZnO (AZO) layers grown in Ar ambient at 200 °C on quartz-glass substrates. Two AZO layers were grown at each thickness, one with and one without a 20-nm-thick ZnON buffer layer grown at 300 °C in Ar/N2 ambient. Plots of the 10-K sheet concentration ns vs d for buffered (B) and unbuffered (UB) samples give straight lines of similar slope, n = 8.36 x 1020 and 8.32 x 1020 cm-3, but different x-axis intercepts, δd = -4 and +13 nm, respectively. Thus, the electrical thicknesses are d - δd = d + 4 and d - 13 nm, respectively. Plots of ns vs d at 294 K produced substantially the same results. Plots of μ vs d can be well fitted with the equation μ(d) = μ(infinity symbol)/[1 + d*/(d-δd)], where d* is the thickness for which μ(infinity symbol) is reduced by a factor 2. For the B and UB samples, d* = 7 and 23 nm, respectively, showing the efficacy of the ZnON buffer. Finally, from n and μ(infinity symbol) we can use degenerate electron scattering theory to calculate bulk donor and acceptor concentrations of 1.23 x 1021 cm-3 and 1.95 x 1020 cm-3, respectively, and Drude theory to predict a plasmonic resonance at1.34 μm. The latter is confirmed by reflectance measurements.
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D. C. Look, K. D. Leedy, A. Kiefer, B. Claflin, N. Itagaki, K. Matsushima, I. Suhariadi, "Model for thickness dependence of mobility and concentration in highly conductive ZnO", Proc. SPIE 8626, Oxide-based Materials and Devices IV, 862602 (18 March 2013); doi: 10.1117/12.2001287; https://doi.org/10.1117/12.2001287
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