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Thickness-dependent polarization modulation at AlN interlayers in GaN heterostructures revealed by atomic-scale
Jiamin Tian1, Fangren Shen1, Yitian Gu1
1Shenzhen Pinghu Laboratory, No. 93, Xinsha Avenue, Pinghu Street, Longgang District, Shenzhen, 518111, China. heguangze@phlab.com.cn.
Nanoscale
|December 16, 2025
Summary
Optimizing aluminum nitride (AlN) interlayers in Gallium Nitride (GaN) high-electron-mobility transistors (HEMTs) is key for performance. Sub-nanoscale AlN thickness critically affects polarization fields and electron gas concentration, guiding device design.
Area of Science:
- Materials Science
- Condensed Matter Physics
- Semiconductor Device Physics
Background:
- High-performance Gallium Nitride (GaN)-based high-electron-mobility transistors (HEMTs) rely on the two-dimensional electron gas (2DEG) concentration.
- Polarization fields at heterojunction interfaces, influenced by interlayers like Aluminum Nitride (AlN), are crucial for 2DEG induction.
- Understanding the atomic-scale, thickness-dependent polarization modulation of AlN interlayers, especially below 1 nm, is essential for optimizing HEMT performance.
Purpose of the Study:
- To characterize polarization fields at AlGaN/AlN/GaN interfaces with sub-nanoscale AlN interlayers (0.5 nm and 1 nm).
- To establish atomic-scale correlations between AlN interlayer thickness, strain, and polarization fields.
- To uncover sub-nanoscale critical size effects influencing 2DEG concentration and HEMT performance.
Main Methods:
- Utilized four-dimensional scanning transmission electron microscopy (4D-STEM) for atomic-scale characterization.
- Employed geometric phase analysis to investigate strain transfer at the interfaces.
- Performed quantitative analyses to determine polarization fields and charge densities.
Main Results:
- A 1 nm AlN interlayer resulted in two opposite electric fields, while a 0.5 nm interlayer showed a single unidirectional field.
- Significant strain transfer was observed with a 0.5 nm AlN interlayer, with minimal strain at the lower AlGaN interface.
- The 1 nm AlN interlayer exhibited stronger polarization fields and higher negative polarization charge density, correlating with lower on-resistance and higher 2DEG concentration.
Conclusions:
- Atomic-scale understanding of AlN interlayer thickness is critical for modulating polarization fields and strain.
- Sub-nanoscale AlN interlayers exhibit critical size effects impacting 2DEG concentration.
- This research provides insights for designing high-performance HEMTs by optimizing AlN interlayer parameters.
