Abstract
Significant improvements in the efficiency of optoelectronic devices can result from the exploitation of nanostructures. These require optimal nanocharacterization techniques to fully understand and improve their performance. In this study we employ room temperature cathodoluminescence hyperspectral imaging to probe single GaN-based nanorods containing multiple quantum wells (MQWs) with a simultaneous combination of very high spatial and spectral resolution. We have investigated the strain state and carrier transport in the vicinity of the MQWs, demonstrating the high efficiencies resulting from reduced electric fields. Power-dependent photoluminescence spectroscopy of arrays of these nanorods confirms that their fabrication results in partial strain relaxation in the MQWs. Our technique allows us to interrogate the structures on a sufficiently small length scale to be able to extract the important information.
Highlights
The rapid development of optoelectronic devices based on group III-nitride semiconductors in the last two decades has demonstrated their considerable potential for applications such as advanced solid-state lighting (SSL) [1, 2]
A typical Secondary electron (SE) micrograph of the nanorod array after the etching procedure is shown in figure 1(a), where the sample is viewed at 45◦ (figure 1(b))
A line scan through the multiple quantum wells (MQWs) emission intensity showed a simple exponential behaviour, allowing us to estimate a carrier diffusion length in the GaN rod at room temperature
Summary
The rapid development of optoelectronic devices based on group III-nitride semiconductors in the last two decades has demonstrated their considerable potential for applications such as advanced solid-state lighting (SSL) [1, 2]. The use of semi-polar and non-polar planes offers one route to reducing the influence of the QCSE [6, 7] Nanostructures, such as nanorods or nanowires, are reported to have enhanced performance due to additional quantum confinement, a reduction in the QCSE due to strain relaxation, and an improvement in light extraction [8,9,10]. In contrast to other studies, the simultaneous combination of high spatial and spectral resolution provided by the CL technique makes it possible to obtain useful information from a single isolated nanostructure on a length scale approaching 10 nm [11, 12]. The emphasis in this study is on simultaneous combination of high spatial and spectral resolution, with most previous reports employing pan-/monochromatic CL imaging or spot-mode CL
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