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

Satoko Toyama; Takehito Seki; Yuya Kanitani; Yoshihiro Kudo; Shigetaka Tomiya; Yuichi Ikuhara; Naoya Shibata

doi:10.1016/j.ultramic.2022.113538

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

Ultramicroscopy. 2022 Aug:238:113538. doi: 10.1016/j.ultramic.2022.113538. Epub 2022 Apr 28.

Authors

Satoko Toyama¹, Takehito Seki², Yuya Kanitani³, Yoshihiro Kudo³, Shigetaka Tomiya³, Yuichi Ikuhara⁴, Naoya Shibata⁵

Affiliations

¹ Institute of Engineering Innovation, School of Engineering, University of Tokyo, 2-11-16, Yayoi, Bunkyo, Tokyo 113-0032, Japan.
² Institute of Engineering Innovation, School of Engineering, University of Tokyo, 2-11-16, Yayoi, Bunkyo, Tokyo 113-0032, Japan; PRESTO, Japan Science and Technology Agency, 4-1-8 Honcho, Kawaguchi, Saitama, 332-0012, Japan. Electronic address: seki@sigma.t.u-tokyo.ac.jp.
³ Sony Group Corporation, 4-14-1, Asahi-cho, Atsugi, Kanagawa, 243-0014, Japan.
⁴ Institute of Engineering Innovation, School of Engineering, University of Tokyo, 2-11-16, Yayoi, Bunkyo, Tokyo 113-0032, Japan; Nanostructures Research Laboratory, Japan Fine Ceramics Center, 2-4-1, Mutsuno, Atsuta, Aichi, 456-8587, Japan.
⁵ Institute of Engineering Innovation, School of Engineering, University of Tokyo, 2-11-16, Yayoi, Bunkyo, Tokyo 113-0032, Japan; Nanostructures Research Laboratory, Japan Fine Ceramics Center, 2-4-1, Mutsuno, Atsuta, Aichi, 456-8587, Japan. Electronic address: shibata@sigma.t.u-tokyo.ac.jp.

PMID: 35567966
DOI: 10.1016/j.ultramic.2022.113538

Abstract

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.