Abstract
A multi-timescale hybrid model is proposed to study microscopically the degraded performance of electronic devices, covering three individual stages of radiation effects studies, including ultra-fast displacement cascade, intermediate defect stabilization and cluster formation, as well as slow defect reaction and migration. Realistic interatomic potentials are employed in molecular-dynamics calculations for the first two stages up to 100 ns as well as for the system composed of layers with thicknesses of hundreds of times the lattice constant. These quasi-steady-state results for individual layers are input into a rate-diffusion theory as initial conditions to calculate the steady-state distribution of point defects in a mesoscopic-scale layered-structure system, including planar biased dislocation loops and spherical neutral voids, on a much longer time scale. Assisted by the density-functional theory for specifying electronic properties of point defects, the resulting spatial distributions of these defects and clusters are taken into account in studying the degradation of electronic and optoelectronic devices, e.g., carrier momentum-relaxation time, defect-mediated non-radiative recombination, defect-assisted tunneling of electrons and defect or charged-defect Raman scattering as well. Such theoretical studies are expected to be crucial in fully understanding the physical mechanism for identifying defect species, performance degradations in field-effect transistors, photo-detectors, light-emitting diodes and solar cells and in the development of effective mitigation methods during their microscopic structure design stages.
Highlights
Point defects are produced by the displacements of atoms from their lattice sites, (Was, 2007; Sigmund, 2006) where the atom displacements are mainly induced by a Primary Knockout Atom (PKA) on a time scale shorter than 50 ps
One of the effective calculation methods for studying the non-thermal spatial-temporal distributions of radiation-induced point defects is the Molecular-Dynamics (MD) model based on a stepped time-evolution approach, which involves the total force by summing over the interatomic potentials from all the atoms in a finite system (Gao et al, 2009)
A density-functional theory is introduced for specifying electronic properties of point defects and four device physics models are employed for characterizing and understanding defect-assisted resonant tunneling, reduced carrier mobility, non-radiative recombination with defects and inelastic light scattering by charged defects
Summary
Point defects (vacancies and interstitial atoms) are produced by the displacements of atoms from their lattice sites, (Was, 2007; Sigmund, 2006) where the atom displacements are mainly induced by a Primary Knockout Atom (PKA) on a time scale shorter than 50 ps. One of the effective calculation methods for studying the non-thermal spatial-temporal distributions of radiation-induced point defects is the Molecular-Dynamics (MD) model based on a stepped time-evolution approach ( termed the collisional and thermal spike stages), which involves the total force by summing over the interatomic potentials from all the atoms in a finite system (Gao et al, 2009). A density-functional theory is introduced for specifying electronic properties of point defects and four device physics models are employed for characterizing and understanding defect-assisted resonant tunneling, reduced carrier mobility, non-radiative recombination with defects and inelastic light scattering by charged defects.
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