GaN-based nanowires hold great promise for solid state lighting applications because of their waveguiding properties and the ability to grow nonpolar GaN nanowire-based heterostructures, which could lead to increased light extraction and improved internal quantum efficiency, respectively. In addition, GaN nanowires can be grown directly on Si substrates, providing an inexpensive and scalable platform for device fabrication. In this talk, we will compare the external quantum efficiency of III-nitride light-emitting diodes (LEDs) based on axial and radial nanowire heterostructures and review our recent results on the controlled growth of III-nitride nanowire heterostructures. Extraction efficiency was calculated using finite-difference time domain photonic simulations and the internal quantum efficiency (IQE) was estimated based on the relative rates of non-radiative, radiative and Auger recombination. We find that m-directional axial heterostructures have the highest extraction efficiency, primarily due to the strong polarization anisotropy of III-nitrides. Furthermore, despite higher surface recombination rates, m-directional axial heterostructures display similar or higher IQE than c-directional axial heterostructures due to lower radiative recombination efficiency in polar c-plane quantum wells caused by the quantum-confined Stark effect. In addition, we have developed a simple, yet powerful, approach to modulate both the diameter and composition of individual III-V nitride nanowires by adjusting in-situ the nanowire seed particle composition and volume. By elucidating the underlying mechanisms controlling structural evolution, we demonstrated the synthesis of m- and c-directional axial InN/InGaN nanowire heterojunctions. With this work, we provide important guidelines for the design of future III-nitride nanowire-based LEDs with high overall efficiencies.

III-nitride nanowire light-emitting diodes: Understanding efficiency and controlled growth

246th National Meeting (2013)

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