Effects of oxygen on low-temperature growth and band alignment of ZnO/GaN heterostructures

Journal Article · Sat Nov 15 00:00:00 EST 2008 · Journal of Vacuum Science and Technology. A, International Journal Devoted to Vacuum, Surfaces, and Films

DOI:https://doi.org/10.1116/1.2990853· OSTI ID:21192518

Liu, H F; Hu, G X; Gong, H; Zang, K Y; Chua, S J ^[1]

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1. Institute of Materials Research and Engineering (IMRE), 3 Research Link, Singapore 117602 (Singapore)

Continuous ZnO thin films have been grown at low temperature (400 deg. C) on GaN/c-sapphire substrates in a radio-frequency magnetron-sputtering chamber employing a substoichiometric ZnO target with and without extra oxygen feeding. The effects of oxygen on the growth and band alignment of the ZnO/GaN heterostructures were investigated by using scanning-electron microscopy, x-ray diffraction, photoluminescence and transmittance/absorbance, ultraviolet-resonant Raman scattering, and x-ray photoelectron spectroscopy. Very remarkable changes of the structural and optical properties resulted from the introduction of oxygen: the surface hexahedral facets were diminished; the size of the surface islands and, hence, the compressive strains were reduced; ultraviolet transparency of the ZnO film was enhanced, together with an increased band gap due to the reduced intrinsic shallow-donor defects; and hence, the free-electron concentration. The offset in valence bands of the ZnO/GaN heterostructure was increased by {approx}90 meV at certain conditions. This is likely due to the increased Ga-O bonds at the ZnO/GaN interface by the incorporation of extra oxygen at the initial growth of ZnO.

• OSTI ID: 21192518
• Journal Information: Journal of Vacuum Science and Technology. A, International Journal Devoted to Vacuum, Surfaces, and Films, Vol. 26, Issue 6; Other Information: DOI: 10.1116/1.2990853; (c) 2008 American Vacuum Society; Country of input: International Atomic Energy Agency (IAEA); ISSN 1553-1813
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ALIGNMENT
ELECTRONS
GALLIUM NITRIDES
HETEROJUNCTIONS
LIGHT TRANSMISSION
MAGNETRONS
OPACITY
OXYGEN
PHOTOLUMINESCENCE
RADIOWAVE RADIATION
SAPPHIRE
SCANNING ELECTRON MICROSCOPY
SEMICONDUCTOR MATERIALS
TEMPERATURE RANGE
THIN FILMS
ULTRAVIOLET RADIATION
ULTRAVIOLET SPECTRA
X-RAY DIFFRACTION
X-RAY PHOTOELECTRON SPECTROSCOPY
ZINC OXIDES