PhD Defense of NIFA Iliass

This thesis aims at studying the electrical characterization and modelling of two-
dimensional (2D) electron gas in MOS-HEMT devices based on the hetero-junction
AlGaN/AlN/GaN. These devices are very promising candidates for power electronics
applications. This research work provides the production team with detailed data on
phenomena affecting GaN material. The goal is to understand precisely how 2D electron gas works and evaluate its electronic transport properties. A new methodology has been developed to identify residual doping of the GaN layer. This method was developed in order to answer a real need to know this doping to determine the quality of the epitaxial GaN layer.
The second research priority was to provide reliable measurement techniques and modelling of the transport properties of 2D electron gas. Within this framework, the split-CV and Hall effect measurements were carried out by providing for each of them a suitable experimental protocol, with an innovative set-up for Hall effect measurements. In addition, this experimental work was supported by modelling the transport properties of 2DEG based on Kubo-Greenwood's formalism. Finally, a more general aspect aimed at an in-depth understanding of the electrostatic stacking of the GaN-MOS-HEMT gate. It is based on C-V electrical characterization, modelling and parameter extraction. This developed model highlights the impact of polarization surface charges and defects on the threshold voltage of MOS-HEMT. This model also contributed to the estimation of the value of deformation in epitaxial GaN layers on a Silicon substrate.