Collaboration framework and context:

AlGaN/GaN HEMT (high Electron Mobility Transistor) have lately drawn great interest for high power (automotive market) and high frequency applications (RF market). To improve performance and reduce the cost of such devices, the CEA-LETI develops a pilot process line of innovative structures (HEMT, Schottky Diodes) on epitaxial GaN on silicon wafers. Although the GaN technology offers a performance gain compared to Si technologies, it also suffers from specific degradations such as current collapse effects which increase the On-state resistance. This phenomena is known to be associated with trapping effects occurring in the HEMT structure during large voltage stress, leading to dynamic change of the HEMT transport and switching properties. The PhD student will focus on the characterization/modeling of the current collapse related trapping phenomena and on the improvement of the HEMTs performance through process steps modifications.

Work description:

The PhD candidate will join the LCTE (Electrical Test and Characterization Laboratory) of the CEA-LETI. Strong collaboration with the LC2E (Electronic Devices for Energy Laboratory) is intended to provide a feedback to device development group. This work will follow different axis.

Firstly, trapping phenomena in AlGaN/GaN HEMTs and MIS capacitors structures (on wafer or packaged) will be characterized. The candidate will have access to electrical characterization equipment dedicated to power electronics (pulsed IV, high voltage C(V), dynamic RDS,ON tester, Thermography imaging…) and also to CMOS related techniques such as CV/GV, Emission Microscopy, Low Frequency Noise. This topic will focus on determining the properties of the active defects such as their localization (interface, volume…) or their energy levels (via temperature dependent measurements).

Secondly, the candidate will have to focus on determining the origin of this traps (stacking faults, dislocations, neutral/ionized impurities…) and to propose process improvement paths (passivation layers, epitaxial growth parameters, insulator materials…). TCAD simulations and analytical modeling will be investigated to improve HEMTs design and to provide a support to electrical characterization.

Excellent skills in semiconductor physics are required as well as a taste for experimental and team work

This position is open until it is filled.

Department: Département Composants Silicium (LETI)
Laboratory: Laboratoire de Caractérisation et Test Electrique
Start Date: 01-10-2015
ECA Code: SL-DRT-15-0572
Contact: william.vandendaele<στο>cea.fr