Dislocation evolution and cyclic hardness enhancement of GaAs induced by cyclic nanoindentation with different shape indenters

Gallium arsenide (GaAs) is a representative III–V semiconductor widely used in optoelectronics and quantum devices, yet its intrinsic brittleness makes it highly susceptible to nanoscale damage. To elucidate its cyclic deformation mechanisms, this study employs molecular dynamics simulations to investigate cyclic nanoindentation of GaAs using spherical, conical, and Berkovich indenters. Results reveal that distinct indenter geometries induce fundamentally different defect evolution pathways: the spherical indenter promotes progressive dislocation pile-up, the conical indenter delays plasticity and favors localized dislocation activation, while the Berkovich indenter triggers dense dislocation nucleation initially but later shifts toward damage-dissipation-dominated mechanisms. These divergent mechanisms directly govern cyclic hardening behavior. Consequently, the degree of hardness enhancement is strongly geometry-dependent, with spherical indentation producing the most pronounced strengthening, conical indentation leading to moderate hardening, and Berkovich indentation exhibiting limited strengthening due to stress relaxation and dislocation constraint. These findings highlight the critical role of indenter geometry in tailoring defect evolution and cyclic strengthening in GaAs, offering atomic-scale insights into the reliability of brittle semiconductor devices.