AVS 57th International Symposium & Exhibition
    Energy Frontiers Topical Conference Thursday Sessions
       Session EN+SS+TF-ThA

Paper EN+SS+TF-ThA9
Deposition of Al-doped ZnO by Atomic Layer Deposition Using Ozone as the Oxygen Source

Thursday, October 21, 2010, 4:40 pm, Room Mesilla

Session: Transparent Conductors
Presenter: W.L. Gladfelter, University of Minnesota
Authors: W.L. Gladfelter, University of Minnesota
H. Yuan, University of Minnesota
B. Luo, University of Minnesota
S.A. Campbell, University of Minnesota
Correspondent: Click to Email
Transparent conducting oxide (TCO) films are used in many photovoltaic and optoelectronic devices. The need to deposit conformal films at relatively low temperature has raised interest in atomic layer deposition (ALD). Literature reports establish that n-doped zinc oxide has been deposited by ALD using water as the source of oxygen and aluminum or gallium as the dopant. The interest in replacing water with ozone has led to many new ALD routes to metal oxide films, including ZnO. In this presentation we will describe an effective ALD route to Al-doped ZnO. Aluminum-doped ZnO (AZO) films were grown on Si and SiO2/Si substrates in the temperature range from 150 - 300°C using diethylzinc as the zinc precursor and ozone as the oxygen source. Trimethylaluminum was used as the aluminum precursor. Two approaches to doping were studied. In one a nanolaminate was formed by interspersing a trimethylaluminum/ozone cycle in between the diethylzinc/ozone cycles. The overall aluminum concentration depended on the number of diethylzinc/ozone cycles. The second approach involved co-injection of both metal precursors in which their relative concentrations were controlled by adjusting the precursor vessel temperature. The influence of the deposition method on the composition, structural, electrical, and optical properties of the AZO films as a function of doping metal concentration will be reported. X-ray diffraction patterns showed all the samples were polycrystalline and exhibited preferential (0001) orientation. The (0002) reflection for AZO films shifted in opposite directions depending on the deposition method. The carbon content of the films was below the detection limit of Auger electron spectrometry. The lowest resistivity (6×10-4 Ω•cm) of the AZO films was obtained using the co-injection process. The average optical transmission was over 85 % in the range of 400-800 nm and the optical band gap increased with increasing doping in accordance with Burstein-Moss effect. The resistivity of AZO films grown by the co-injection method decreased to 3×10-4 Ω•cm after rapid thermal annealing (RTA) in an Ar atmosphere.