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

Abstract

Abstract. The dependences of the 294 and 10 K mobility μ and volume carrier concentration n on thickness (d ¼ 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 n s versus d for buffered (B) and unbuffered (UB) samples give straight lines of similar slope, n ¼ 8.36 × 10 20 and 8.32 × 10 20 cm −3 , but different x -axis intercepts, δd ¼ −4 and þ13 nm, respectively. Plots of n s versus d at 294 K produce substantially the same results. Plots of μ versus d can be well fitted with the equation μðd Þ ¼ μð∞Þ∕½1 þ d à ∕ðd − δdÞ, where d à is the thickness for which μð∞Þ is reduced by a factor 2. For the B and UB samples, dà ¼ 7 and 23 nm, respectively, showing the efficacy of the ZnON buffer. Finally, from n and μð∞Þ we can use degenerate electron scattering theory to calculate bulk donor and acceptor concentrations of 1.23 × 10 21 cm −3 and 1.95 × 10 20 cm −3 , respectively, and Drude theory to predict a plasmonic resonance at 1.34 μm. The latter is confirmed by reflectance measurements.

Microstructure evolution of Al-doped zinc oxide and Sn-doped indium oxide deposited by radio-frequency magnetron sputtering: A comparison

“…From the fitting parameters, the product of the mean free electron path l e and the diffuse reflection coefficient (1-p) is obtained, shown in Table I. For comparison data of Look et al 31 for ZnO:Ga films have been also included and fitted (Look et al used the same model without referring to the FuchsSondheimer theory). The mean free path can be calculated also from the carrier concentration n and the resistivity q 1 according to the Drude-Sommerfeld model of the free electron gas 30 where h is Planck's constant and e is the elementary charge…”

Contrasting transparent conductive properties of ZnO films on amorphous and crystalline substrates in view of thickness dependence

“…However, only a few papers have reported on transparent conductive ZnO films on epitaxial substrates. 16 In the work reported in this paper, we conducted comparative studies on a-SiN x :H films and glass substrates to judge whether the thickness dependence of the resistivity of Gadoped ZnO (GZO) films deposited on them is a universal characteristic of amorphous substrates. We also investigated how the epitaxial template substrate affects the crystallinity and electric conductivity of ZnO films.…”

Significant mobility enhancement in extremely thin highly doped ZnO films

“…However, while a good buffer layer can mitigate lattice-mismatch effects, it can never do so perfectly, as manifested by an increase in mobility l as thickness d increases. This phenomenon has been reported by a large number of workers over the last decade [2][3][4][5][6][7][8][9][10][11] and can often be characterized by a simple phenomenological formula [8][9][10][11] …”