Electronic Properties of Extended Defects in Germanium: A First-Principles Study

Germanium, thanks to its high carrier mobility and potential for direct band gap engineering, is a promising material for advanced electronic, optoelectronic, and quantum technologies. Yet, its epitaxial growth on silicon often leads to extended defects like dislocations and stacking faults, long considered inevitable and detrimental. These defects alter germanium's electronic properties. Leveraging ab initio calculations and machine learning-based interatomic potentials, we explore their impact in detail. Dislocations, modeled as dipoles under periodic boundary conditions, introduce trap states within the band gap, potentially affecting devices, but also offering opportunities to engineer optical and spin features. Our findings indicate that such defects, rather than mere drawbacks, could be exploited to tailor germanium's optoelectronic behavior, paving the way for novel quantum and photonic applications.