The Foton Institute invites you to the presentation of doctoral thesis work:
Advanced DFT modeling of surfaces and interfaces for the
monolithic integration of III-V semiconductors on Si
Sreejith PALLIKKARA CHANDRASEKHARAN
under the supervision of Laurent PEDESSEAU and Charles CORNET
This public defense will occur wednesday 29th October 2025 at 09H30;
Amphithéâtre GCU, Bat. 7, INSA Rennes
Zoom link to attend the Defense online :
https://cnrs.zoom.us/j/96513807462?pwd=DX6ZKxAFPuRBWTAX0wBvVrkFQjXUOu.1
meeting ID: 965 1380 7462
key: w8J4i4
Summary:
This thesis explores the atomic-scale epitaxial growth mechanisms of III-V semiconductors on
Si(001) for applications in photonics and energy, using density functional theory (DFT). However, direct epitaxy remains challenging due to defects such as anti-phase boundaries and misfit dislocations. To address these challenges, this work develops a first-principles framework based on DFT to calculate absolute surface and interface energies in III-V/Si systems, enabling a quantitative evaluation of wetting behavior and interface thermodynamics. GaP/Si is studied as a model system to analyze the wetting behavior, revealing that an inevitable passivation on Si prior to epitaxy promotes 3D Volmer-Weber
growth. A theoretical model for APB formation is then proposed, identifying these defects as metastable features formed as a consequence of island coalescence. Additionally, an ab initio Wulff-Kaischew construction is implemented to predict the equilibrium crystal shapes showing good agreement with in situ TEM observations of GaP/Si epitaxial growth. Notably, a novel fictitious charge passivation on surfaces scheme is introduced to accurately compute interface energies, effectively eliminating difficulties and errors from complex surface reconstructions. This method is applied first to biaxially strained, and next to 90° misfit dislocations of GaAs/Si systems, revealing energetically favorable dislocation core structures with charge compensation. Furthermore, preliminary calculations of the electronic band structure of this heterostructure structure reveal the presence of mid-bandgap states, which are associated with both dislocations and interfaces. Overall, this work advances the atomic-scale understanding and control of III-V/Si integration, offering new tools for optimizing next-generation multifunctional devices, while also providing a new perspective on these heterostructures.