Molecular beam epitaxial (MBE) growth

Vertically aligned self-organized AlInN/GaN heterostructures and AlInN core-shell nanowire LEDs were grown on Si(111) substrates by radio-frequency plasma-assisted molecular beam epitaxy. An extremely high-purity nitrogen generation system was employed to introduce ultrahigh-quality nitrogen gas to the RIBER RF-nitrogen plasma cell. This system includes a Delux nitrogen purifying system with a bypass assembly life status indicator, valve control for bypass and a purifier and heating control. The oxide on the substrate surface was desorbed in situ at 780 °C. First, GaN nanowire templates were formed under nitrogen-rich conditions without the use of any external catalyst. The growth conditions of the GaN nanowires included a growth temperature of 770 °C, a nitrogen flow rate of 1.0 sccm, a forward plasma power of 400 W, and a Ga beam equivalent pressure of 6 × 10⁻⁸ Torr. To achieve UV light emission, self-organized AlInN segments were subsequently grown on top of the GaN nanowires. The In composition in the active region could be controlled by varying the In and Al beam flux and/or the substrate temperature. The growth temperature of the AlInN active regions was varied to enhance the In incorporation, which was controlled between 670 °C and 720 °C. During the epitaxial growth of AlInN segments, the nitrogen flow rate and plasma power were maintained at 2.5 sccm and 400 W, respectively.