Structural and Raman properties of compositionally tunable AlxGa1−xN (0.66 ≤ x ≤ 1) nanowires

In this work, we describe compositionally tunable AlxGa1−xN nanowires (0.66 ≤ x ≤ 1) grown on Si (1 0 0) substrates using a chemical vapor deposition (CVD) process. The composition of AlxGa1−xN nanowires may be tuned by adjusting the vapor temperature of the AlCl3 and GaCl3 used in its production. The structural, chemical and optical properties of the AlxGa1−xN nanowires are investigated using X-ray diffractometry (XRD), field emission scanning electron microscopy (FESEM), X-ray energy-dispersive spectroscopy (EDS), transmission electron microscopy (TEM) and Raman spectroscopy. All the AlxGa1−xN nanowires exhibit a preferred c-axis orientation. Raman analysis shows that the E22 phonon exhibits two-mode behavior. The positions of the AlN-like E22, GaN-like E22 and A1(TO) modes shift toward higher frequencies as the amount of Al increases. The growth of these AlxGa1−xN nanowires has been proposed to follow a vapor-solid-solid (VSS) mechanism.