Research Projects

Phase Diagram of Grain Boundary Facet and Line Junctions in Silicon

Faceting of grain boundaries has a strong impact on the properties of structural, functional, and optoelectronic materials. In this project, we employ density-functional theory and modified embedded atom method calculations to investigate the energetics and thermodynamic stability of facets and line junctions in Silicon. We find that higher energy metastable GB phases can be stabilized by thermodynamics and not kinetics when constituting the facets at line junctions. This is in contrast to the common perception that the properties of faceting are merely driven by the anisotropic GB energies. more

Growth and Properties of V-pit Defects on Wurtzite GaN Polar Surfaces

The fundamental mechanisms of V-pits formation on epitaxially grown GaN polar surfaces are investigated combining state-of-the-art first-principles calculations and elasticity theory.
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Substitutional Synthesis of sub-nm Thick InGaN QWs

The synthesis of InGaN digital alloys in the form of short period InGaN/GaN superlttices is investigated by combining ab/initio and empirical potential calculations with PAMBE growth , Photoluminescence Spectroscopy, and HR(S)TEM characterization. more

Dislocation Induced Nanopipe Formation in GaN

Screw dislocation induced nanopipes are investigated by combining elasticity theory with density functional theory calculations. Based on these calculations a c-type screw dislocation phase diagram is constructed which describes the energetically most favorable core structures as function of the Ga, N and H chemical potentials. We find that nanopipes with diameters ranging from ≈1 to ≈2 nm are energetically favorable for high values of the H chemical potential and conditions that correspond to MOCVD and MOVPE growth. more

Phase diagram of III-Nitride ternary alloys

III-Nitride alloys such as InN, GaN, and AlN dominate the optoelectronics industry with applications in light emitting devices (LED), laser diodes (LD), and power electronics and constitute one of the most important semiconducting materials nowadays. In this project the bulk thermodynamics of these alloys are investigated. more

Effects of surface hybridization on epitaxially grown alloys

The effect of surfaces and more specifically of surface reconstruction and rehybridization on the properties, composition, ordering and thermal stability of epitxailly grown alloys is investigated. more

Asymmetric Line Segregation at Faceted Si Grain Boundaries

The energetics as well as atomistic mechanisms underlying the segregation of impurities at Si grain boundaries (GB) and GB junctions have been investigated. more