Rutherford backscattering/channeling study of a thin AlGaN layer on Al 2O 3(0 0 0 1)

Abstract

A thin AlGaN layer, which is suitable for structural study using Rutherford backscattering (RBS)/channeling, was grown on an Al 2O 3(0 0 0 1) substrate by metalorganic chemical vapor deposition. The results show that the composition of the epilayer is Al 0.05Ga 0.95N and that although the epilayer is very thin (79 nm), it has a good crystalline quality ( χ min=1.9%). The azimuthal orientation of the AlGaN epilayer relative to the Al 2O 3 substrate is AlGaN[0 0 0 1] // Al 2O 3[0 0 0 1] and AlGaN {1 1 2 ̄ 0} // Al 2 O 3{1 0 1 ̄ 0} , showing that the AlGaN epilayer is rotated by 30° around the [0 0 0 1] axis with respect to the Al 2O 3 substrate which decreases the lattice mismatch between the epilayer and the substrate significantly. RBS angular scan was used to determine the strain-induced tetragonal distortion of the epilayer. Combined with X-ray diffraction, the perpendicular and parallel elastic strains of the AlGaN layer, e ⊥=+0.31% and e ∥=−0.28%, can be calculated.