GaN Transistors for next generation RF mobile communications: are they reliable?

GaN-on-Silicon Enhancement-mode MOS-HEMTs are central to the evolution of high-efficiency, high-frequency RF power amplifiers for mobile communications, including emerging 6G technologies. While GaN-on-Si platforms offer promising power handling capabilities and cost advantages, device reliability remains a major barrier to commercial deployment, particularly in enhancement-mode configurations required for low-power mobile systems.

One of the critical reliability issues arises from defects in high-k dielectrics, which lead to unwanted charge trapping and emission processes. These instabilities degrade device performance over time, limiting both efficiency and operational lifetime. The aim of this PhD project is to systematically investigate and isolate the dominant defect mechanisms contributing to these effects in complex MOS-HEMT structures.

Research Objectives:

• Identify, characterize and model key defect states responsible for charge trapping/emission behavior.
• Understand how device stability evolves as a function of temperature, voltage and time.
• Correlate stability behavior to the physical and electrical properties of the GaN channel, (back-)barrier layers, and high-k gate dielectrics to isolate physical location of defects responsible for instabilities.
• Support the development of material and process strategies aimed at reducing intrinsic defect densities and improving overall device stability.

Methodology:

The project will combine device-level electrical measurements, such as transient and steady-state stress testing, with physics-based modeling of trapping/emission dynamics. You will work closely with material scientists and process engineers to evaluate the impact of fabrication choices on defect formation and behavior.  Access to advanced characterization techniques (including TCAD simulations) will be provided.

Candidate Profile:

We welcome applications from candidates with a strong background in Electrical Engineering, Physics, or Materials Science. Prior experience in semiconductor device physics, reliability analysis, or wide bandgap materials (especially GaN) is advantageous, but not mandatory. A passion for deep technical problem-solving and multidisciplinary research is essential.

This project offers an excellent opportunity to contribute to cutting-edge device research with real-world applications in future wireless communication systems. The successful candidate will gain valuable experience in semiconductor technology, reliability physics, and materials characterization, with opportunities for publication and conference participation.​