DONG Li-pu, LIU Yu-xue, XU Chang-shan, LIU Yi-chun, LI Ya-jun. High Quality Mg<sub>x</sub>Zn<sub>1-x</sub>O Films Fabricated by Electron Beam Evaporation Combined with Heat Treatment[J]. Chinese Journal of Luminescence, 2008,29(2): 313-317
DONG Li-pu, LIU Yu-xue, XU Chang-shan, LIU Yi-chun, LI Ya-jun. High Quality Mg<sub>x</sub>Zn<sub>1-x</sub>O Films Fabricated by Electron Beam Evaporation Combined with Heat Treatment[J]. Chinese Journal of Luminescence, 2008,29(2): 313-317DOI:
High Quality MgxZn1-xO Films Fabricated by Electron Beam Evaporation Combined with Heat Treatment
O alloys as a promising candidate for applications in optoelectronic devices in the ultraviolet region. ZnO is a wide-band-gap semiconductor with a direct gap of ~3.37 eV. The band gap becomes even larger if Zn atoms are substituted by Mg atoms
which have a similar ionic radius
allowing the construction of ZnO/Mg
x
Zn
1-x
O quantum-well and superlattice devices. One of the important problems that limits the fabrication of Mg
x
Zn
1-x
O alloy is the fact that the thermodynamic solubility limit of MgO in ZnO is about 4%. The problem of Mg concentration in ZnO is excess of 4% without phase segregation is important and necessary to be studied in details.In this paper
Mg
x
Zn
1-x
O films with wurtzite-type structure were fabricated on quartz substrates at 150℃ by electron beam evaporation (EBE) using Mg
0.15
Zn
0.85
O target combined with heat treatment. The depen-dence of the microstructure and optical properties of Mg
x
Zn
1-x
O films on the annealing conditions and cooling modes has been investigated using X-ray diffraction (XRD)
scanning electron microscope (SEM)
absorption and photoluminescence (PL) spectra. In the XRD spectra
no diffraction peaks belonging to MgO were observed. The results showed that Mg
x
Zn
1-x
O films were single wurtzite-type structure. The increasing band gap is not due to quantum confinement effect according to SEM images
but attributed to the formation of Mg
x
Zn
1-x
O alloy films. In the absorption spectra
the blueshift of absorption edges and absorption peaks indicated that the band gap of Mg
x
Zn
1-x
O films was tuned from 3.37 eV to 3.61 eV by changing annealing conditions and cooling modes. As it can be seen
the full-width at half-maximum of the XRD peak for Mg
x
Zn
1-x
O films annealed at 700℃ followed with rapid cooling increases
which indicated the Zn
2+
ions in ZnO lattice were successfully substituted by Mg
2+
ions. Accordingly
an evident blueshift is observed in photoluminescence spectra for the Mg
x
Zn
1-x
O films annealed at 700℃ followed with rapid cooling
and the PL intensity of near-band-edge (NBE) emission is much higher than that of its visible emission
showing that high quality Mg
x
Zn
1-x
O films were obtained.We controlled on the Mg
2+
concentration by changing annealing conditions and cooling modes. By using rapid cooling at high annealing temperature
the high-quality Mg
x
Zn
1-x
O films were achieved. The fabrication of high-quality Mg
x
Zn
1-x
O films makes it possible to obtain light detecting and emitting devices in the UV region.
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