Model for thickness dependence of mobility and concentration in highly conductive ZnO

D. C. Look; K. D. Leedy; A. Kiefer; B. Claflin; N. Itagaki; K. Matsushima; I. Suhariadi

doi:10.1117/12.2001287

18 March 2013 Model for thickness dependence of mobility and concentration in highly conductive ZnO

D. C. Look, K. D. Leedy, A. Kiefer, B. Claflin, N. Itagaki, K. Matsushima, I. Suhariadi

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 n_s 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 n_s 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.

Citation Download Citation

D. C. Look, K. D. Leedy, A. Kiefer, B. Claflin, N. Itagaki, K. Matsushima, and 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); https://doi.org/10.1117/12.2001287

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