Time-Resolved Cathodoluminescence in an UTEM applied to III-V heterostructures

The development of time-resolved Cathodoluminescence (TR-CL) in a scanning electron microscope enabled the measurement of the lifetime of excited states in semiconductors with a sub-wavelength spatial resolution. It was used for example to measure the influence of stacking faults on the GaN exciton ¹, to probe the role of a silver layer on the dynamics of a YAG crystal ² or to show the influence of stress on the optical properties of ZnO nanowires ³. These results demonstrate that TR-CL is essential to study the correlation between semiconductor optical and structural properties (composition, defects, strain…). While all these pioneering studies were done using a scanning electron microscope, the improvement of the spatial resolution and the combination with other electron-based spectroscopies offered by transmission electron microscopes will be a step forward for TR-CL. We recently succeed to do the first time-resolved cathodoluminescence experiments within an ultrasfast transmission electron microscope. They were performed in a unique microscope, based on a cold-FEG electron gun ⁴. This technology allows among other things to reach a spatial resolution of a few nanometres, essential for the study of III-V heterostructures.
In this presentation we will discuss our latest results on InGaN quantum wells and discuss the unique features and opportunities of this technique.
References
1.          Corfdir, P. et al. Exciton localization on basal stacking faults in a-plane epitaxial lateral overgrown GaN grown by hydride vapor phase epitaxy. J. Appl. Phys. 105, 043102 (2009).
2.          Moerland, R. J., Weppelman, I. G. C., Garming, M. W. H., Kruit, P. & Hoogenboom, J. P. Time-resolved cathodoluminescence microscopy with sub-nanosecond beam blanking for direct evaluation of the local density of states. Opt. Express 24, 24760 (2016).
3.          Fu, X. et al. Exciton Drift in Semiconductors under Uniform Strain Gradients: Application to Bent ZnO Microwires. ACS Nano 8, 3412–3420 (2014).
4.          Houdellier, F., Caruso, G. M., Weber, S., Kociak, M. & Arbouet, A. Development of a high brightness ultrafast Transmission Electron Microscope based on a laser-driven cold field emission source. Ultramicroscopy 186, 128–138 (2018).