Growth and characterization of ternary AlGaN alloy nanocones across the entire composition range

AlGaN ternary alloys have unique properties suitable for numerous applications due to their tunable direct band gap from 3.4 to 6.2 eV by changing the composition. Herein we report a convenient chemical vapor deposition growth of the quasi-aligned Al_xGa_1-xN alloy nanocones over the entire composition range. The nanocones were grown on Si substrates in large area by the reactions between GaCl₃, AlCl₃ vapors, and NH₃ gas under moderate temperature around 700 °C. The as-prepared wurtzite Al_xGa_1-xN nanocones have single-crystalline structure preferentially growing along the c-axis, with homogeneous composition distribution, as revealed by the characterizations of electron microscopy, X-ray diffraction, energy-dispersive X-ray spectroscopy, and selected area electron diffraction. The continuous composition tunability is also demonstrated by the progressive evolutions of the band edge emission in cathodoluminescence and the turn-on and threshold fields in field emission measurements. The successful preparation of Al_xGa_1-xN nanocones provides the new possibility for the further development of advanced nano- and opto-electronic devices.