In situ hydrogen doping of titanium dioxide via PAALD for enhanced MIM diode performance in high-frequency applications

Abstract

Metal–insulator–metal (MIM) diodes based on black titanium dioxide are fabricated and characterized for the first time by in situ hydrogen doping via plasma assisted atomic layer deposition (PAALD). Hydrogen-doped Pt/H–TiO_x/Al diodes with varying hydrogenation times are compared to undoped Pt/TiO₂/Al and nitrogen-doped Pt/N–TiO_x/Al diodes. The hydrogen atoms are expected to produce oxygen vacancies and modify the bandgap of TiO₂, therefore changing the conduction mechanisms of the diodes. This leads to enhanced electron transport and improved performance of the hydrogen-doped diodes. The representative figures of merit observed for a Pt/H–TiO_x/Al diode with 3 s hydrogenation time include a resistance of ∼10⁴ Ω and a responsivity of 0.65 A W⁻¹. Notably, the H–TiO_x diodes exhibited a substantial reduction in resistance (10⁴–10⁵ Ω) compared to pristine TiO₂ diodes (10¹⁰–10¹¹ Ω). The N–TiO_x diodes showed intermediate resistance levels (10⁵–10⁷ Ω). This defect-engineering approach is found to reduce diode resistance without negatively impacting the figure of merit. The study demonstrates that in situ hydrogen doping of TiO₂ using PAALD is a promising method for enhancing the performance of MIM diodes in high-frequency applications, potentially advancing the development of THz and other advanced electronic technologies.