N‐Type Behavior from a P‐Type Dopant: Charge Compensation Mechanisms in Trivalent Y‐Doped HfO$_ 2$

The current market launch of HfO$_ 2$ -based ferroelectric devices relies on the control of the inherent oxygen vacancies (OVs) and their impact on the ferroelectric performance. Due to the necessary stabilization of the ferroelectric phase by doping, several dopants are investigated for their applicability to control the vacancy concentration. Hf mathematical equation signatures in X-ray photoemission spectra are often used as an indication of OVs for both qualitative and quantitative analysis. The analysis of Y doped HfO$_ 2$ (Y:HfO$_ 2$) as investigated by hard x-ray photoelectron spectroscopy (HAXPES) reveals the inapplicability of the Hf mathematical equation signature for a quantitative determination of OVs in the case of heterovalent doping and is restricted to pure HfO$_ 2$ or isoelectronic substitution of Hf by, for example, Zr.