First-principles study of hydrogen-related defects at the a-SiO2/Si(100) interface

During the fabrication and annealing of amorphous SiO2/Si interfaces, hydrogen is commonly introduced to passivate interfacial dangling bonds, yet it may also generate electrically active hydrogen-related defects. Here, first-principles calculations are performed to systematically investigate the structural evolution and electronic properties of hydrogen-related defects at ten representative sites within the suboxide region of an amorphous SiO2/Si(100) interface under neutral and charged conditions. To eliminate spurious long-range Coulomb interactions arising from periodic boundary conditions in charged-defect calculations, electrostatic energy corrections are implemented by combining density functional theory with a classical finite-element solution of the Poisson equation. Corrected charge transition levels are subsequently determined for all defect configurations. The results suggest that electrostatic corrections can induce substantial shifts in charge transition levels, with maximum deviations reaching 0.44 eV. For most defect sites, only one thermodynamically active charge transition level is found to be located within the silicon band gap for most of the sampled defect configurations. In addition, the formation energies of hydrogen-related defects are found to span a wide range from 1.71 to 5.23 eV, exhibiting a clear dependence on the spatial position of defects within the interfacial suboxide layer. These results provide insight into the charge behavior and thermodynamic stability of hydrogen-related defects at amorphous SiO2/Si interfaces, offering an atomistic foundation for understanding their potential impact on device performance and reliability.