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Gallium and indium co-doping of epitaxial zinc oxide thin films grown in water at 90 °C

2011; Institute of Physics; Volume: 44; Issue: 12 Linguagem: Inglês

10.1088/0022-3727/44/12/125104

1361-6463

Hong Quang Le, Soo Jin Chua,

Gas Sensing Nanomaterials and Sensors

Zinc oxide (ZnO) thin films were intentionally co-doped with group III elements (gallium) in order to investigate and understand the effects of co-doping on the morphological, electrical and optical properties of gallium-doped ZnO (GZO) films. The co-doped films were grown on MgAl 2 O 4 spinel substrates using a low-temperature solution-phase method known as hydrothermal synthesis. Gallium with indium co-doped ZnO (GIZO) films displayed a dramatic improvement in surface morphology as compared with the Ga-doped ZnO (GZO) films due to the compensation effect of gallium and indium doping which reduced the lattice strain. The 0.0033M gallium with 3.3 × 10 −4 M indium co-doped film exhibited an electron concentration of 3.14 × 10 20 cm −3 and resistivity of 7.4 × 10 −4 Ω cm which were both enhancements of 1.5 times over the GZO film. These films were comparable to the films fabricated by more expensive and complicated vapour-phase methods. The figure of merit for this film was determined to be 1.63 × 10 −2 sq/Ω which was very close to the indium tin oxide conducting films currently used commercially. Finally, the GIZO film was hydrothermally grown on a p-GaN film to form an n-ZnO/p-GaN heterojunction light-emitting diode (LED). This LED showed diode I – V characteristics and exhibited strong cool-white light emission which signified the prospect of using GIZO as an effective and low-cost n-type layer in LEDs.