Structural and Electrical Properties of Tetravalent-Element-Doped Hf0.5Zr0.5O2 Thin Films

Achieving low-leakage and more symmetric bipolar hysteretic response in low-thermal-budget Hf0.5Zr0.5O2 (HZO) is challenging because phase stability, defect populations, and interfacial transport evolve in a coupled manner. Here, we establish a comparative framework to assess the combined roles of tetravalent dopant selection and bottom interfacial-layer insertion in pulsed-laser-deposited HZO thin films (~ 19 nm) integrated into Pt/HZO/TiN capacitors without post-annealing. Within a common growth window (400 °C), 5 mol% tetravalent dopants (Si, Ti, Sn, and Pb) redistribute the apparent balance between monoclinic and non-monoclinic contributions in a dopant-dependent fashion. However, a larger non-monoclinic fraction does not translate proportionally into electrically active polarization reversal. Si doping yields the largest apparent hysteresis opening but also the highest leakage, whereas Sn shows a reduced hysteretic response despite comparable structural fractions, indicating a decoupling between diffraction-derived phase redistribution and functional switching volume. In a separate Si:HZO subset grown at an oxygen partial pressure (pO2) of 20 mTorr, interfacial-layer insertion provides an independent design axis: a 1 nm ZrO2 layer increases the non-monoclinic fraction and promotes apparent hysteresis opening, while increasing the thickness to 2 nm reverses the structural trend. In contrast, a 1 nm Al2O3 interlayer strongly suppresses leakage but yields a monoclinic-dominant signature and reduced hysteresis. Overall, these results show that phase redistribution alone is insufficient under constrained thermal budgets; defect-mediated transport and interfacial injection barriers critically limit the electrically active switching volume, motivating co-optimization of bulk composition and interface design for backend-compatible HZO stacks.