The spatial resolution of cathodoluminescence (CL) has been limited in the past by the SEM resolution available at low-voltages (>3 kV). By utilising the state-of-the-art low-voltage SEM, the maximum spatial resolution of CL can be achieved. Here, the characterisation of individual InGaN nanoclusters using low-voltage CL will be presented.
The samples used in these experiments were hexagonal InGaN/GaN light-emitting diode microwires grown on sapphire using MOCVD where, during the growth, indium has been made to segregate on the nanowire to form InGaN nano-clusters of varying sizes and composition. CL measurements were performed using an FEI Verios 460 FEG-SEM equipped with a Gatan MonoCL4 system for the detection of CL emission. CL signal was detected using a high-speed photo-multiplier tube (HSPMT) for the collection of CL images or a UV-enhanced CCD array for the collection of full CL spectra.
Low-voltage CL imaging and full-spectral mapping has been used to characterise the indium clustering on these microwires. Individual spectra were able to be collected from InGaN nanoclusters with separations of less than 50 nm. From the characterisation of individual InGaN nanoclusters, “quantum-dot-like” emissions can be identified.
This work demonstrates that through the use of state-of-the-art SEM, the maximum spatial resolving power of CL can be achieved. This has been utilised to characterise the optical emissions form individual InGaN nanoclusters.
This work is supported by the Australian Research Council and performed in part at the ACT node of the Australian National Fabrication Facility, a company established under the National Collaborative Research Infrastructure Strategy to provide nano and micro-fabrication facilities for Australia’s researchers. The authors acknowledge Dr. M. Lysevych for assistance in MOCVD growth.