MBE growth of cubic Al yGa 1− yN/GaN heterostructures—structural, vibrational and optical properties

Abstract

Cubic Al y Ga 1− y N/GaN heterostructures on GaAs(0 0 1) substrates were grown by radio-frequency plasma-assisted molecular beam epitaxy. High resolution X-ray diffraction, micro-Raman, spectroscopic ellipsometry, and cathodoluminescence measurements were used to characterize the structural, optical and vibrational properties of the Al y Ga 1− y N epilayers. The AlN mole fraction y of the alloy was varied between 0.07< y<0.20. X-ray diffraction reciprocal space maps demonstrate the good crystal quality of the cubic Al y Ga 1− y N films. The measured Raman shift of the phonon modes of the Al y Ga 1− y N alloy was in excellent agreement with theoretical calculations. Both SE and CL of the Al y Ga 1− y N epilayer showed a linear increase of the band gap with increasing Al-content.