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

Area of Science:

• Materials Science
• Condensed Matter Physics
• Electron Microscopy

Background:

• Differential phase contrast (DPC) in scanning transmission electron microscopy (STEM) visualizes electric fields.
• Diffraction contrast in crystalline specimens complicates electric field mapping.
• Conventional methods fail to reduce diffraction contrast in distorted heterostructures like GaN-based devices.

Purpose of the Study:

• To develop a method for suppressing diffraction contrast in STEM-DPC imaging of crystalline heterostructures.
• To enable quantitative electric field mapping in GaN/AlGaN multi-heterostructures.

Main Methods:

• Averaging multiple DPC signals acquired under various beam-tilt conditions near the zone axis.
• Quantitative estimation of residual diffraction contrast using simulations.

Main Results:

• The developed technique effectively suppresses diffraction contrast in STEM-DPC imaging.
• Quantitative electric field distributions were successfully obtained for GaN/AlGaN multi-heterostructures.
• Residual diffraction contrast was quantitatively estimated and its potential error contribution analyzed.

Conclusions:

• The novel DPC signal averaging method overcomes limitations of conventional techniques for electric field mapping in crystalline materials.
• This approach facilitates accurate, quantitative analysis of electric fields in complex semiconductor devices.
• The findings are crucial for understanding and designing advanced GaN-based electronic devices.