Atomistic nonequilibrium Green's function study of radiation-induced charge loss in floating gate flash memories

Abstract

This study presents an atomistic nonequilibrium Green's function (NEGF) approach for modeling radiation-induced charge loss in floating-gate flash memories, which become increasingly vulnerable to radiation effects as device features shrink. Nonradiative charge-carrier recombination at localized deep-level defect centers is treated by coupling the defect Green's function to delocalized interface states derived from a two-probe tight-binding description, via multiphonon-scattering self-energies. Using oxygen vacancies as representative deep-level traps, the trap-assisted tunneling current under retention conditions is calculated by integrating the NEGF formalism within a drift-diffusion solver. This NEGF framework significantly improves agreement with experimental data from heavy-ion irradiation, and provides insights beyond semiclassical models. These findings underscore the necessity of atomistic, fully quantum treatments for reliable assessment and design of radiation-hardened nonvolatile memory technologies.