IM3-P-8 Surface and sub-surface defect analysis in semiconductors by Secondary Electron Emission Spectroscopy and local charge transport mapping

Semiconductor defects, on one side, undermine functionality and reliability of devices, on the other side, defects may offer the possibility to be engineered to develop peculiar quantum-like effects. In both cases high resolution, non-destructive means of characterisation are necessary. Prevailing semiconductor defect characterisation techniques are destructive, like TEM, or lack nanometric spatial precision for localised defect investigation. To address this, we explore Electron Beam-Induced Current (EBIC) for defect characterization within scanning electron microscopy (SEM). However, EBIC’s limited spatial resolution restricts nanoscale defect investigation. Here, we propose secondary electron emission spectroscopy (SEES) to overcome this limitation. SEES correlates secondary electron spectra with valence band density of states[1]. Defects perturb the local electronic structure, necessitating detailed probing of these modifications, could potentially be viable with SEES. Integrating SEES with bulk-sensitive EBIC offers a comprehensive framework to study defect-induced charge transport and emission mechanisms. The investigated Ge-Si photodiodes serve as a model heterostructure for EBIC and SEES measurements, where epitaxial strain-induced dislocations emerge at the interface and grow into the bulk germanium[2]. These dislocations act as electrically active centers, mediating carrier recombination, and generation, thereby influencing device performance. We adopted a commercial SEM, integrating it with a custom-designed secondary electron energy analyzer, employed to acquire SEES spectra. The experimental apparatus can be configured as an add-on for commercial SEMs. Dislocation mapping in Ge-Si p-i-n diodes via EBIC revealed their electrical activity. SEES was performed on test samples to calibrate the energy analyzer. Future work includes room-temperature and low-temperature SEES for dislocation contrast, alongside low-temperature EBIC measurements using a custom-designed cooling stage for concurrent surface and bulk characterization. Ultimately, this work seeks to establish SEES as a viable nanoscale defect analysis technique by benchmarking it against EBIC, thereby assessing its reliability in resolving defect-induced electrical activity with nanometer spatial precision. [1] Han W et al. Sci Rep. 2020;10(1):22144. [2] Osmond J et al. Thin Solid Films. 2008;517(1):380-382.