| AVS 59th Annual International Symposium and Exhibition | |
| Transparent Conductors and Printable Electronics Focus Topic | Thursday Sessions |
| Session TC+EM+AS+TF+EN-ThM |
| Session: | Transparent Conductors and Devices |
| Presenter: | K. Sharma, Eindhoven University of Technology, The Netherlands |
| Authors: | K. Sharma, Eindhoven University of Technology, The Netherlands H.C.M. Knoops, Eindhoven University of Technology, The Netherlands M.V. Ponomarev, Eindhoven University of Technology, The Netherlands R. Joy, Roth and Rau BV, Germany M. Velden, Roth and Rau BV, Germany D. Borsa, Roth and Rau BV, Germany R. Bosch, Roth and Rau BV, Germany W.M.M. Kessels, Eindhoven University of Technology, The Netherlands M. Creatore, Eindhoven University of Technology, The Netherlands |
| Correspondent: | Click to Email |
Session: Transparent Conductors and Devices
The ever-increasing demand for transparent conducting oxides (TCO) for application in flat panel displays, light emitting diodes (LEDs), and thin film photovoltaics drives the present research in the field of TCOs. Aluminum-doped zinc oxide (ZnO:Al) is often referred to as a potential alternative to e.g. indium tin oxide. The ZnO:Al is considered appealing due to the relatively low cost, high abundance, non-toxicity, resistance to H2 etching and, under specific conditions, surface texturing for light management/trapping. Thin ZnO:Al films (~ 100 nm) with low resistivity (2-5 * 10-4 ohm*cm) along with high transmission (> 85 %) are desirable in many devices. Furthermore, large area processing/ high throughput are essential pre-requisites for industrial applications.
ZnO:Al thin films (< 150 nm) have been deposited by using an in-line industrial expanding thermal plasma chemical vapor deposition (ETP-CVD) technique,1,2,3 by means of O2/diethylzinc/trimethylaluminium mixtures. High diethyl zinc flow rate conditions2 were applied, which enable the development of a conductive ( 5·10-4 Ω·cm), 300 nm-thick ZnO:Al layer by promoting the development of a densely packed structure at early stages of growth, as very recently reported.2
In the present contribution, the effect of the dopant, i.e. trimethylaluminium, is investigated to further improve the electrical quality of even thinner ZnO:Al layers. ZnO:Al films were analyzed with spectroscopic ellipsometry, four point probe, hall measurements, X-ray photon spectroscopy (XPS), Rutherford backscattering (RBS), elastic recoil backscattering (ERD), and X-ray diffraction (XRD).
A remarkable low resistivity of 5 ·10-4 Ω·cm was measured for a ZnO:Al film with thickness of only 120 nm, characterized by a carrier concentration of 1 ·1021 cm-3, with an electron mobility in the range of 10-25 cm2/V ·s.2,3 The obtained mobility values are higher than previously reported value of 13 cm2/V ·s for 300 nm thick ZnO:Al.2 The improvement in terms of conductivity is attributed to the large hydrogen content (2-4 ·1021 at/cm3) promoting the chemical passivation of the grain boundaries.
A broad characterization of highly conductive thin ZnO:Al films along with insights on charge transport process will be presented.
Reference List
1. B. Hoex et al., Progress in Photovoltaics 13, 705 (2005).
2. M. V. Ponomarev et al. Journal of Applied Physics 112, 043708 (2012).
3. M. V. Ponomarev, et al. , Journal of Applied Physics 111, 063715 (2012).