CIFRE - Cosmic rays robustness - H/F

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YOUR ROLE

Since 2000, wide-bandgap materials, especially silicon carbide, have been progressively introduced into power electronic circuits. Owing to their higher critical electric field compared with silicon, high-voltage unipolar devices such as Schottky diodes and MOS transistors have been developed, replacing silicon bipolar devices, including fast bipolar diodes and IGBTs, with significantly reduced switching losses.

The resulting improvement in power efficiency reduces cooling requirements and enables a smaller overall system footprint, making the adoption of wide-bandgap devices particularly advantageous in applications with stringent constraints on size and weight, such as spacecraft and avionics. For these applications, high tolerance to cosmic rays is obviously expected.

On the ground, higher power efficiency is also crucial for electrical vehicle deployment as it increases driving range, and for smart-grid applications that require very high voltage devices (> 2000V). Here again, cosmic ray robustness, especially neutrons, is essential to meet the very low failure rates expected in the automotive sector and to avoid complex maintenance in smart-grid applications.

Since 2004, cosmic rays impact on silicon carbide devices has been extensively studied. In addition to the well-known single event burnout (SEB), also observed in silicon power devices, silicon carbide devices have been shown to exhibit a new cumulative degradation mechanism reported as single-event leakage current (SELC). No consensus has yet been reached within the scientific community regarding its cause.

In this context, you'll be responsible for :

• Defining models to be implemented in cosmic-ray simulations for silicon carbide devices.

• Performing simulations on existing diode structures to validate the simulation setup. This activity will benefit from an ongoing study engaged with the french national center for space studies (CNES), which will provide with heavy-ion robustness results from different diode structures.

• Studying the reverse characteristics of damaged diodes and request analyses (either electrical or structural ones) to understand the mechanisms involved.

• Simulating new diode structures to improve cosmic-ray robustness.

YOUR SKILLS & EXPERIENCES

• Master degree in semiconductor physics, condensed-matter physics, or particle-matter interaction,

• B2 English level and finite-elements simulation experience would be appreciated.

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