Nitride Semiconductor Nanorod Heterostructures for Full-Color and White-Light Applications

Development of full-color and white light-emitting diodes (LEDs) and laser diodes (LDs) is tremendously important for energy-efficient lighting and advanced display applications. At present, the InGaN/GaN semiconductor heterostructure system is considered as the most promising device candidate for these applications because the direct band gap of In_xGa_1 − xN spans from the near-infrared (NIR) to the near-UV, including the complete visible spectrum. However, there are severe issues related to structural imperfection and polarization effects in high-In-content InGaN/GaN semiconductor heterostructures, resulting in low emission efficiency in the long-wavelength spectral region (beyond blue). To overcome the formidable material challenges in InGaN/GaN semiconductor heterostructures, many studies reported recently have suggested a promising solution based on full-color and white solid-sate emitters using one-dimensional (1D) nitride semiconductor nanostructures (nanorods, nanowires, nanocolumns, nanopillars, nanotubes, etc.). Especially, vertically self-aligned GaN nanorod arrays have been applied as strain-free or strain-reduced growth templates for heteroepitaxial growth of InGaN/GaN nanorod heterostructures emitting in the full visible spectrum. Moreover, 1D nitride semiconductor nanorod heterostructures can be grown by plasma-assisted molecular beam epitaxy and metal-organic vapor phase epitaxy with well-defined axial/radial geometries and abruptly modulated compositions to achieve unique device functionalities. In this chapter, we give a detailed discussion about nitride semiconductor nanorod heterostructures, including polarization effects, nanorod growth and polarity control, doping and surface properties, nanorod heterojunction band alignments, axial nanorod heterostructures for full-color and tunable white LEDs, as well as green and full-color core–shell nanorod plasmonic nanolasers. Some future perspectives will also be given for both fundamental studies and new device applications of nitride semiconductor nanorod heterostructures.