Arrays of dislocation free uniform Ga-polar GaN columns have been realized on patterned SiO x /GaN/sapphire templates by metal organic vapor phase epitaxy using a continuous growth mode. The key parameters and the physical principles of growth of Ga-polar GaN three-dimensional columns are identified, and their potential for manipulating the growth process is discussed. High aspect ratio columns have been achieved using silane during the growth, leading to n-type columns. The vertical growth rate increases with increasing silane flow. In a core–shell columnar LED structure, the shells of InGaN/GaN multi quantum wells and p-GaN have been realized on a core of n-doped GaN column. Cathodoluminescence gives insight into the inner structure of these core–shell LED structures.

In the past few years, tremendous progress has been demonstrated on epitaxial growth and processing of group III nitride nano‐ and microrods (NAMs). This has also enabled the fabrication of optoelectronic devices based on NAMs as active elements. However, their efficiency is still far behind the performance of conventional GaN‐based light emitting diodes (LEDs). This Review presents the most recent activities on the growth and processing of NAMs exhibiting a core–shell geometry, i.e. structures which consist of an active region shell layer wrapped around a three‐dimensional (3D) core, which allow for an enormous increase in active area compared to planar technology. The most common growth approaches using metalorganic vapour phase epitaxy are described and evaluated with particular regard to their potential for solid state lighting applications. Examples for the unique properties of 3D NAMs are presented including their excellent crystalline quality. Furthermore, factors limiting the overall performance of 3D core–shell LEDs are revealed and the potential of overcoming these limitations are discussed. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

We have investigated the radiative properties of InGaN disks in GaN nanowires grown by plasma enhanced molecular beam epitaxy on (001) silicon substrates. The growth of the nanowire heterostructures has been optimized to maximize the radiative efficiency, or internal quantum efficiency (IQE), for photoluminescence emission at λ = 650 nm. It is found that the IQE increases significantly (by ∼10%) to 52%, when post-growth passivation of nanowire surface with silicon nitride or parylene is applied. The increase in efficiency is supported by radiative- and nonradiative lifetimes derived from data obtained from temperature dependent- and time-resolved photoluminescence measurements. Light emitting diodes with p-i-n disk-in-nanowire heterostructures passivated with parylene have been fabricated and characterized.