Aluminium incorporation in polar, semi- and non-polar AlGaN layers: a comparative study of x-ray diffraction and optical properties

<jats:title>Abstract</jats:title><jats:p>Growth of Al<jats:sub><jats:italic>x</jats:italic></jats:sub>Ga<jats:sub>1−<jats:italic>x</jats:italic></jats:sub>N layers (0 ≤ <jats:italic>x</jats:italic> ≤ 1) simultaneously on polar (0001), semipolar (<jats:inline-formula><jats:alternatives><jats:tex-math>$$10\bar{{\rm{1}}}$$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mn>10</mml:mn> <mml:mover> <mml:mn>1</mml:mn> <mml:mo>¯</mml:mo> </mml:mover> </mml:math></jats:alternatives></jats:inline-formula>3) and (<jats:inline-formula><jats:alternatives><jats:tex-math>$$11\bar{{\rm{2}}}2$$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mn>11</mml:mn> <mml:mover> <mml:mn>2</mml:mn> <mml:mo>¯</mml:mo> </mml:mover> <mml:mn>2</mml:mn> </mml:math></jats:alternatives></jats:inline-formula>), as well as nonpolar (<jats:inline-formula><jats:alternatives><jats:tex-math>$$10\bar{{\rm{1}}}0$$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mn>10</mml:mn> <mml:mover> <mml:mn>1</mml:mn> <mml:mo>¯</mml:mo> </mml:mover> <mml:mn>0</mml:mn> </mml:math></jats:alternatives></jats:inline-formula>) and (<jats:inline-formula><jats:alternatives><jats:tex-math>$$11\bar{{\rm{2}}}0$$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mn>11</mml:mn> <mml:mover> <mml:mn>2</mml:mn> <mml:mo>¯</mml:mo> </mml:mover> <mml:mn>0</mml:mn> </mml:math></jats:alternatives></jats:inline-formula>) AlN templates, which were grown on planar sapphire substrates, has been investigated by metal-organic vapour phase epitaxy. By taking into account anisotropic in-plane strain of semi- and non-polar layers, their aluminium incorporation has been determined by x-ray diffraction analysis. Optical emission energy of the layers was obtained from room-temperature photoluminescence spectra, and their effective bandgap energy was estimated from room-temperature pseudo-dielectric functions. Both x-ray diffraction and optical data consistently show that aluminium incorporation is comparable on the polar, semi- and non-polar planes.</jats:p>