Assessment of Active Dopants and p–n Junction Abruptness Using In Situ Biased 4D-STEM

• Published in: Nano letters 2022-12, Vol.22 (23), p.9544-9550
• Main Authors: da Silva, Bruno César, Sadre Momtaz, Zahra, Monroy, Eva, Okuno, Hanako, Rouviere, Jean-Luc, Cooper, David, Den Hertog, Martien Ilse
• Format: Article
• Language: English
• Subjects: Engineering Sciences; Micro and nanotechnologies; Microelectronics
• ISSN: 1530-6984; 1530-6992
• DOI: 10.1021/acs.nanolett.2c03684

A key issue in the development of high-performance semiconductor devices is the ability to properly measure active dopants at the nanometer scale. In a p–n junction, the abruptness of the dopant profile around the metallurgical junction directly influences the electric field. Here, a contacted nominally symmetric and highly doped (N A = N D = 9 × 1018 cm–3) silicon p–n specimen is studied through in situ biased four-dimensional scanning transmission electron microscopy (4D-STEM). Measurements of electric field, built-in voltage, depletion region width, and charge density are combined with analytical equations and finite-element simulations in order to evaluate the quality of the junction interface. It is shown that all the junction parameters measured are compatible with a linearly graded junction. This hypothesis is also consistent with the evolution of the electric field with bias as well as off-axis electron holography data. These results demonstrate that in situ biased 4D-STEM can allow a better understanding of the electrostatics of semiconductor p–n junctions with nm-scale resolution.