Growth and optical polarization properties of high-quality AlN and AlGaN/AlN quantum wells

Abstract

High-quality AlN and AlₓGa₁₋ₓN/AlN multiple quantum wells (MQWs) (x>0.69) were fabricated by modified migration enhanced epitaxy based on metalorganic vapor phase epitaxy, and their structural and optical polarization properties were studied. High-quality AlN was confirmed by narrow x-ray diffraction (XRD) linewidth and for MQWs from satellite peaks, Al composition, well and barrier widths were estimated. Photoluminescence spectroscopy revealed predominant polarization direction in ~1.5-nm-thick QWs switched from GaN-like E⊥c to AlN-like E∥c at x~0.83. This x much higher than ever reported is due to strain and quantum confinement effects on valence band ordering. Decreasing the well width also promotes E⊥c polarization.