Description of the thesis topic

To face the multiple challenges of the energy transition, whether at the generation, transport or use of electricity, extremely efficient electronic components are necessary. Thus, new components are developed from gallium nitride (GaN) to manufacture fast switches and rectifiers that can withstand high voltages for reduced component sizes compared to those manufactured with Silicon.
However, all these components that should reduce energy losses during all stages of electricity transformation remain difficult to manufacture in large quantities at low cost. Whether for consumer applications below 220 V, or for electric or hybrid vehicles between 600 and 1200V, the epitaxial deposition of semiconductors such as GaN on large diameter substrates is a key point to lower manufacturing costs. For this purpose, silicon substrates are used as a support, but the large differences in crystalline properties (lattice parameters, expansion coefficients) between GaN and Silicon are at the origin of crystalline defects and mechanical stresses harmful to a controlled manufacturing of high-performance components. To address this issue, the project aims at developing new stacks of epitaxial layers containing Gallium Nitride (GaN) on Silicon substrate to demonstrate a power transistor capable of withstanding voltages higher than 1200 V.
In particular, the project aims to remove the limitations related to the breakdown that usually requires the use of very thick GaN films. These ideas were the subject of a first proof of principle at lower voltage (500 V) with thin films. Technical difficulties remain however for the realization of optimal epitaxial layers, in accordance with this new approach and able to withstand a voltage of 1400 V. The proposed thesis will explore the different epitaxial strategies by MBE, MOVPE or their combination. Within this project funded by the French National Research Agency (ANR), the company III-V lab will provide support with the epitaxy of structures by MOVPE. The LN2 laboratory will conduct design activities through simulations and manufacture test components. The electrical characterizations in continuous and pulsed modes will be carried out under high voltage at LAAS to demonstrate the advantages of these new devices.

Work Context

The proposed thesis will take place at CRHEA (Valbonne, 06). It will focus on the epitaxy of these new structures using MBE and MOVPE techniques and their structural and electrical characterizations which will be validated by the partners through the manufacturing and characterization of test devices.

The position is located in a sector under the protection of scientific and technical potential (PPST), and therefore requires, in accordance with the regulations, that your arrival is authorized by the competent authority of the MESR.

Additional Information

To carry out these studies, skills in the fields of material science, solid-state physics, and micro-nano manufacturing would be a major asset.