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0957-K10-47

Optical and Electrical Properties of Gallium-Doped Mg15Zn85O Thin Films Wei Wei1, Vikram Bhosle1, Chunming Jin2, and Roger J Narayan2 1 Materials Science and Engineering, North Carolina State University, 3030 Engineering Building I, 911 Partners Way, Raleigh, NC, 27695-7907 2 Biomedical Engineering, North Carolina State University, 3030 Engineering Building I, 911 Partners Way, Raleigh, NC, 27695-7115 ABSTRACT Ga-doped Mg0.15Zn0.85O thin films have been grown on fused silica substrates at 350 °C with four different gallium concentration values using pulsed laser deposition. X-ray diffraction results indicate that these films were textured with c-plane parallel to the substrate surface. The bandgap of the films were determined based on the absorption measurements. The bandgaps of the Ga-doped thin films shifted to higher energy with respect to that of the unalloyed Mg0.15Zn0.85O thin film due to the band filling effect of electron distribution in the conduction band. Resistivity of the films was measured with four-point probe at temperatures from 295 K to 15 K. The activation energy of the gallium dopants was extracted by fitting the temperature dependent curve of resistivity. INTRODUCTION The research interests on transparent conducting oxides have been increased significantly in recent years.1-2 These materials have the applications for opto-electronic devices such as light emitting diodes, flat-panel displays, and solar cells.2 Currently, indium-tin oxide is the material used for most of the transparent conducting oxide applications. However, use of indium-tin oxide has been limited by the short supply and high cost of indium. Its thermal characteristics of indium-tin oxide also cause problems in certain applications. These drawbacks have increased research efforts for exploring other transparent conducting oxide materials. Zinc oxide doped with Group-III metals (e.g., aluminum or gallium) is one of these materials.3 ZnO has a large bandgap of 3.39 eV and good thermal stability.4 In this work, we report the electrical and optical properties of Ga-doped Mg0.15Zn0.85O thin films prepared by pulsed laser deposition. MgxZn1-xO alloys have an increased bandgap as the magnesium content increases.5 Although phase diagram suggested that the solid solubility of magnesium in wurtzite zinc oxide was limited to a maximum of 4 atomic percent, the nonequlibrium nature of pulsed laser deposition has proved that the magnesium concentration higher than 34% can be achieved while the wurtzite structure of ZnO is still retained. The bandgap of Mg0.34Zn0.66O thin film is ~4.28 eV, which is 0.90 eV higher than that of unalloyed ZnO (3.39 eV). EXPERIMENTAL PROCEDURE Ga-doped Mg0.15Zn0.85O were grown on amorphous fused silica substrates by pulsed-laser deposition using a KrF excimer laser (λ=248 nm, ts=25 ns) in a high vacuum chamber. All the depositions were performed at 350 °C for 10 minutes. The ZnO-MgO-Ga2O3 composite targets with four different gallium concentrations (1 at%, 2at%, 2.5 at%, and 3 at%) were used, which