BEOL Compatible Indium-Tin-Oxide Transistors: Switching of Ultrahigh-Density 2-D Electron Gas Over 0.8 x 10¹⁴/cm² at Oxide/Oxide Interface by the Change of Ferroelectric Polarization

In this work, we report back-end-of-line (BEOL) compatible indium-tin-oxide (ITO) transistors with ferroelectric (FE) Hf0.5Zr0.5O2 (HZO) as gate insulator. A tunable high-density 2-D electron gas over 0.8 $\sf \times \,\,10^{14}$ /cm2 is achieved at the HZO/ITO oxide/oxide interface because of the FE polarization, which is confirmed by ${I}$ – ${V}$ , positive up and negative down (PUND), and Hall measurements. Such high carrier density can be completely modulated and switched on and off by FE polarization switching, enabling high mobility ITO transistor with high ON-current and high ON/OFF ratio.