Characteristics of InN grown directly on Al2O3 (0 0 0 1) substrates by pulsed laser deposition

We have grown InN films directly on sapphire (0 0 0 1) substrates by pulsed laser deposition (PLD), without the need for any buffer layers. We have found that the growth temperature and the laser intensity exert a large influence on the crystalline quality of the InN films. We have also found that the electrical properties and the crystalline quality are improved with increasing film thickness. FWHM values for InN 0002 and 112¯4 X-ray rocking curves for a 1.5-μm-thick InN film were as small as 0.14° and 0.26°, respectively. The electron mobility and carrier density in the film were 1300 cm2/V s and 3.0×1018 cm−3, respectively. The fact that PLD direct growth of InN on sapphire substrates leads to formation of epitaxial material is quite consistent with the theoretical prediction from first principles calculations and is probably due to the enhanced surface migration of the InN precursors.