MOVPE growth of AlN and AlGaN films on N-polar annealed and sputtered AlN templates

Abstract

We performed metalorganic vapor phase epitaxy (MOVPE) growth of AlN (MOVPE-AlN) and AlGaN films on N-polar face-to-face annealed and sputtered AlN templates (N-polar FFA Sp-AlN) on sapphire substrates. The off-cut angle of the sapphire substrates was varied from 0.2° to 6.0°. The effects of the off-cut angle on the surface morphology and crystallinity of the N-polar MOVPE-AlN and AlGaN were elucidated. The results showed that the crystallinities of N-polar FFA Sp-AlN and MOVPE-AlN were independent of the off-cut angle. The threading dislocation density (TDD) was estimated to be approximately 5.0 × 108cm−2 by using values of the X-ray rocking curve full-width at half maximum. In comparison, the density of the hillocks on the MOVPE-AlN surfaces was suppressed, and the surface flatness was improved by increasing the off-cut angle of the sapphire substrate. The crystallinity of the AlGaN was improved by increasing the off-cut angle. Our results prove that N-polar AlN and AlGaN films with smooth surfaces and low TDDs could be achieved by MOVPE on N-polar FFA Sp-AlN with a large substrate off-cut angle of 6.0°.