ASTRID - Accompagnement spécifique des travaux de recherches et d’innovation défense


Submission summary

This project meets the following DGA priority: "New components for microwave chains and communication: Miniaturized components, with increased flexibility, up to submillimetric frequencies". The implementation of the GaN power components for a distributed amplification system, especially for frequencies above 30 GHz demands a significant improvement of RF performance in order to be competitive with other viable solutions available in the RF market. However, a successful employment of this technology in industrial sectors requires an in-depth analysis of the reliability of the GaN HEMT devices. Therefore, it is of utmost important to understand the device failure mechanisms and parasitic effects of these devices. In case of GaN HEMT devices grown on silicon carbide substrate, the complexity of trapping mechanisms and the presence of parasitic effects implies that detailed experimental characterization is essential to understand their physical behavior and also the reliability.

The objective of this ambitious project is to demonstrate a systematic methodology of analyzing the device characteristics which establishes a link between the physical device and the design of the circuit. It also aims to make a significant contribution to the understanding of trapping mechanisms responsible for RF performance degradation and device failure of GaN HEMT device technology of the IEMN laboratory (AlN/GaN) and also the UMS foundry (AlGaN/GaN). The comprehensive understanding and identifying the location of traps in the device structure necessitates the concurrent use of physical device simulations and experimental characterizations highlighting the dispersive effects of traps. These trapping and thermal effects are also an important constraint in obtaining the RF performance in terms of linearity and efficiency. The development of precise characterization test-bench for modulated signals is also crucial for the investigation of non-linear distortions.

In GaN HEMT devices, the thermal effects and the capture and emission process of charge carriers are significantly important over a wide frequency range and therefore, it is critical to develop a transistor model integrating these phenomena. The improvement of non-linear models, valid for wide range of operating conditions will ensure the consideration of device parameters (linearity, thermal, noise, efficiency, …) in the system design. To the best of our knowledge, there is no such transistor model for operating at millimeter wave frequencies, usable for low to high power and integrating low-frequency noise sources, thermal and trapping behavior are available. The proposed non-linear electro-thermal compact model, based on the simulation-experimental characterization with excess low-frequency noise sources will be in the form of separate modules, allows a circuit designer to activate or deactivate, depending on the type of application used.

The objective of this project is to resolve the problems inherent in this GaN technology, particularly improving its efficiency and output power and also to establish a control over the charge-trapping mechanisms, in order to obtain the optimal performance of the RF power amplifiers at Ka-band (Gate length of 0.15µm and 0.1µm) and beyond. Moreover, it is also important to understand the trapping phenomenon related to these specific applications and this will help to reduce their impact while optimizing the device technology for achieving maximum power and efficiency. This project also aims to correlate the impact of fabrication process and the topology of the transistors on the effects of traps and this will allow us:

• To understand the relationship between electrical effects of traps and physical structure of the grown devices (GH15) on different epitaxial structures.
• To identify the technological path to mitigate the effects of traps on the electrical performance of RF power amplifiers.

Project coordination

Jean-Christophe NALLATAMBY (Université de Limoges)

The author of this summary is the project coordinator, who is responsible for the content of this summary. The ANR declines any responsibility as for its contents.


IEMN Institut d'électronique, de microélectronique et de nanotechnologie
XLIM Université de Limoges

Help of the ANR 298,221 euros
Beginning and duration of the scientific project: December 2017 - 36 Months

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