Controlled synthesis of nonpolar GaInN/GaN multiple-quantum-shells on GaN nanowires by metal-organic chemical vapour deposition

Abstract

Nonpolar GaInN/GaN multiple-quantum shells (MQSs) on nanowires (NWs) were investigated for high-efficiency light-emitting diodes (LEDs). The growth conditions of NWs were systematically optimized via a continuous growth mode in metal-organic chemical vapour deposition (MOCVD). The In incorporation rate on the m-planes decreased as the growth temperature elaborated, whereas the crystalline quality is improved. The cathodoluminescence (CL) results revealed that longer growth time of the GaInN well can induce additional In-rich droplets and degrade the emission properties of MQSs. The CL emission intensity and the peak wavelength increased as the number of MQS pairs increased from one to three pairs, which was attributed to the increased In incorporation as the diameter enhanced. The linearly enhanced CL emission intensity with barrier thickness was ascribed to the increase of the electron-hole states from the GaN barrier to the wells, resulting in a larger recombination probability. The scanning transmission electron microscopy (STEM) results demonstrated that a thicker barrier shell can suppress the formation of In-rich droplets. Overall, the feasibility of obtaining high-quality m-plane coaxial GaInN/GaN MQSs structures are promising for NW-based white and micro LEDs.