Atomic-Scale Insight into the Amorphous Structure of Al-, Ga-, and Zn-Doped GeSb ₂ Te ₄ Phase-Change Material

With the continued scaling of phase-change memory (PCM), achieving improved data retention and switching reliability critically depends on enhancing the stability of the amorphous phase in Ge–Sb–Te alloys. Using density functional theory combined with ab initio molecular dynamics (AIMD) simulations, we investigate the effects of Al, Ga, and Zn doping on the structural and electronic properties of amorphous GeSb 2 Te 4 . Among the dopants considered, Al incorporation yields the lowest atomic diffusion coefficient (DC) and the smallest max discrepancy of diffusion coefficient, suggesting superior resistance to atomic rearrangement under operating conditions, with an optimal doping concentration of 20%. This enhanced stability is correlated with the formation of stability-favoring local structural motifs, including wrong bonds, tetrahedral coordination units, and 5-fold rings, which are known to impede crystallization kinetics. From a device perspective, 20% Al doping reduces the mobility band gap from 0.69 to 0.61 eV while introducing highly localized band-tail states, implying potential benefits for reduced threshold switching voltage. These results provide atomic-scale insight into dopant-assisted stabilization mechanisms in GeSb 2 Te 4 and offer guidance for the design of phase-change materials with improved endurance and reliability.