Abstract
We report herein on a high degree of wurtzite [11-20] orientation in AlN films heavily doped with Fe (AlFeN). The AlFeN films were deposited by RF sputtering on SiO2 glass and sapphire (0001) substrates. X-ray diffraction measurements revealed the Fe concentration dependence of the preferred orientation of these films. At a high Fe concentration (10–26.1%), the films had a [11-20] orientation, whereas films with less than 5% of Fe had a [0001] orientation. This tendency was evident on sapphire (0001) substrate as well as on the SiO2 glass substrate. The highest degree of [11-20] orientation was achieved for 19.4% of Fe. Transmission electron microscopy observations of the [11-20]-oriented AlFeN films (Fe: 19.4%) showed that randomly oriented nuclei form near the interface with the substrate, and subsequently, columnar grains selectively grow with a [11-20] orientation. These results suggest that AlFeN (11-20) films may be potentially applicable as a buffer layer to grow non-polar AlN on various substrates.
Highlights
Wurtzite aluminum nitride (AlN) is a wide- and direct-band-gap semiconductor (6.1 eV)1 that is a promising material for deep-ultraviolet optoelectronic devices, such as light-emitting diodes (LEDs) or laser diodes (LDs)
AlN single-crystal thin films are generally obtained by epitaxial growth using molecular beam epitaxy (MBE) and chemical vapor deposition (CVD)
Electrostatic fields are spontaneously and/or piezoelectrically generated along the [0001] axis in all wurtzite III nitrides.3–5. These electrostatic fields are not suitable when AlN is employed in LED and surface acoustic wave (SAW) devices because they cause low luminescent efficiency in LED and low conversion efficiency in SAW devices
Summary
Wurtzite aluminum nitride (AlN) is a wide- and direct-band-gap semiconductor (6.1 eV)1 that is a promising material for deep-ultraviolet optoelectronic devices, such as light-emitting diodes (LEDs) or laser diodes (LDs). We have been studying the effects of 3d-transition-metal-doping to AlN on its crystallographic properties after deposition by RF sputtering on SiO2 glass substrates.23–27 In this letter, we report the successful growth of wurtzite [11,12,13,14,15,16,17,18,19,20]-oriented films by heavy Fe doping (higher than 10%) to AlN (AlFeN). The results of X-ray diffraction (XRD) and transmission electron microscopy (TEM) studies for the AlFeN films showed a distinctive change in the growth direction depending on the Fe concentration.
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