Study of dynamic degradation and reliability of advanced GaN on Si power devices

Published : 8 February 2020

GaN-on-Si based power devices are now considered as the next generation of mass market devices for high frequency & low looses power converters (DC/DC, AC/DC or DC/AC). In this vision, LETI is developing its own pîlot line of GaN on Si power devices (CMOS compatible) from the GaN epitaxy to the final power module. These devices are supposed to operate dynamically between high voltage stage (650V and below) and high current state (> 20A) at high frequencies (> 100kHz). Statics and dynamic performances being proved, it is worth of interest to test and study reliability of these devices under high voltage stress and high temperature as well as under practical swithching conditions (hard/soft/ZVS). These studies aim to understand the underlying physical degradation mechanisms arising under operating conditions and ultimately to stabilize the technologie for industrial technological transfer.

The PhD student will be responsible of :

– Finalizing exisiting dynamic setups and create new ones especially concerning on-wafer switching test (limitations/feasibility)

– In Depth study of HEMT electrical parameters degradation (Ron, Vt, Sw…) as well as Diode parameters (Vf, Sw) during DC or AC stress to determine the root cause of the degradation leading to reliability reduction.

– Determination of Switching SOA of GaN based devices from LETI as well as studying new acceleration factors such as duty factor or switching frequency

– Localization and Identification of Failure point and understanding of the Failure root cause through FA studies (IR or visible camera + FIB/MEB studies)

– Proposal of new technological solutions to overcome some early failures and low realiblity issues

The PhD student will be curious, open minded and team worker.

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