Indium incorporation and optical properties of polar, semipolar and nonpolar InAlN

Abstract

Abstract Indium incorporation and the optical properties of In x Al 1− x N layers (0 ≤ x ≤ 0.45) grown by metal-organic vapour phase epitaxy have been investigated simultaneously on polar (0001), untwinned semipolar (101̅3) and nonpolar (101̅0) AlN templates, which were prepared on planar sapphire substrates. The InN mole fraction ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>x</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>InN</mml:mi> </mml:mrow> </mml:msub> </mml:math> ) of the layers was tuned by changing growth temperature from 660°C to 860°C. <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>x</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>InN</mml:mi> </mml:mrow> </mml:msub> </mml:math> determined by x-ray diffraction was found to be comparable for the polar, semipolar and nonpolar surface orientations. This is consistent with comparable effective bandgap energy of the layers obtained from optical transmission measurements at room temperature. The bandgap bowing parameter was found to be strongly composition-dependent. Room-temperature photoluminescence measurements showed impurity transitions for the layers with <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>x</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>InN</mml:mi> </mml:mrow> </mml:msub> </mml:math> ≤ 0.2, while InAlN near-band-edge luminescence was observed for the layers with higher <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>x</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>InN</mml:mi> </mml:mrow> </mml:msub> </mml:math> .