Quantitative electric field mapping in semiconductor heterostructures via tilt-scan averaged DPC STEM

• Published in: Ultramicroscopy 2022-08, Vol.238, p.113538-113538, Article 113538
• Main Authors: Toyama, Satoko, Seki, Takehito, Kanitani, Yuya, Kudo, Yoshihiro, Tomiya, Shigetaka, Ikuhara, Yuichi, Shibata, Naoya
• Format: Article
• Language: English
• ISSN: 0304-3991; 1879-2723
• DOI: 10.1016/j.ultramic.2022.113538

•An effective and practical method to suppress diffraction contrast was developed for differential phase contrast (DPC) scanning transmission electron microscopy.•Tilt-scan averaging DPC method, which acquires DPC signals with various beam-tilt conditions, can effectively suppress diffraction contrast in real-time.•Residual diffraction contrast in the tilt-scan averaging DPC was evaluated using the simulation of channeling maps.•The effectiveness of tilt-scan averaging DPC was demonstrated in electric field imaging of GaN/AlGaN multi-heterostructures. Differential phase contrast (DPC) in scanning transmission electron microscopy can be used to visualize electric field distributions within specimens in real space. However, for electric field mapping in crystalline specimens, the concomitant diffraction contrast is seriously problematic. In particular, for heterostructures with large lattice distortions, such as GaN-based semiconductor devices, the diffraction contrast cannot be reduced using conventional methods such as DPC image acquisition under off-axis conditions. In the present study, the electric field imaging of heterostructures is shown to suppress the diffraction contrast by averaging multiple DPC signals, obtained under various beam-tilt conditions near the zone axis. The remaining diffraction contrast was quantitatively estimated through simulations. This technique was demonstrated to enable the quantitative evaluation of electric field distributions across GaN/AlGaN multi-heterostructures, with errors possibly attributed to the residual diffraction contrast.