Structural and Electrical Properties of Atomic Layer Deposited Al‐Doped ZnO Films |
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| Authors: | Do‐Joong Lee Hyun‐Mi Kim Jang‐Yeon Kwon Hyoji Choi Soo‐Hyun Kim Ki‐Bum Kim |
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| Affiliation: | 1. Department of Materials Science and Engineering, Seoul National University, 599 Gwanak‐ro, Gwanak‐gu, Seoul 151–742, Korea;2. School of Materials Science and Engineering, Yeungnam University, Gyeongsan‐si, Gyeongsangbuk‐do 712–749, Korea;3. WCU Hybrid Materials Program, Department of Materials Science and Engineering, Seoul National University, 599 Gwanak‐ro, Gwanak‐gu, Seoul 151–742, Korea |
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| Abstract: | Structural and electrical properties of Al‐doped ZnO (AZO) films deposited by atomic layer deposition (ALD) are investigated to study the extrinsic doping mechanism of a transparent conducting oxide. ALD‐AZO films exhibit a unique layer‐by‐layer structure consisting of a ZnO matrix and Al2O3 dopant layers, as determined by transmission electron microscopy analysis. In these layered AZO films, a single Al2O3 dopant layer deposited during one ALD cycle could provide ≈4.5 × 1013 cm?2 free electrons to the ZnO. The effective field model for doping is suggested to explain the decrease in the carrier concentration of ALD‐AZO films when the interval between the Al2O3 layers is reduced to less than ≈2.6 nm (>3.4 at% Al). By correlating the electrical and structural properties, an extrinsic doping mechanism of ALD‐AZO films is proposed in which the incorporated Al atoms take oxygen from the ZnO matrix and form doubly charged donors, such as oxygen vacancies or zinc interstitials. |
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| Keywords: | transparent conducting oxides atomic layer deposition Al‐doped ZnO doping mechanisms |
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