Model for thickness dependence of mobility and concentration in highly conductive zinc oxide

David C. Look, D. Leedy Kevin, Kiefer Arnold Kiefer, Claflin Bruce Claflin, Naho Itagaki, Koichi Matsushima, Iping Surhariadi

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39 Citations (Scopus)


The dependences of the 294 and 10 K mobility μ and volume carrier concentration n on thickness (d = 25 to 147 nm) are examined in aluminum-doped zinc oxide (AZO). Two AZO layers are grown at each thickness, one with and one without a 20-nm-thick ZnON buffer layer. Plots of the 10 K sheet concentration ns versus d for buffered (B) and unbuffered (UB) samples give straight lines of similar slope, n = 8.36 × 1020 and 8.32 × 1020 cm-3, but different x-axis intercepts, δd = -4 and +13 nm, respectively. Plots of ns versus d at 294 K produce substantially the same results. Plots of μ versus d can be well fitted with the equation μ(d) = μ(∞)/[1 + d*]/(d - δd)], where d* is the thickness for which μ(∞) 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(∞) we can use degenerate electron scattering theory to calculate bulk donor and acceptor concentrations of 1.23 × 1021 cm-3 and 1.95 × 1020 cm -3, respectively, and Drude theory to predict a plasmonic resonance at 1.34 μm. The latter is confirmed by reflectance measurements.

Original languageEnglish
Article number033801
JournalOptical Engineering
Issue number3
Publication statusPublished - 2013

All Science Journal Classification (ASJC) codes

  • Atomic and Molecular Physics, and Optics
  • General Engineering


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