Impedance matching between the terahertz antenna and ultra-fast Metal-Insulator-Metal (MIM) diode is a crucial issue in realizing rectenna technology for harvesting infrared (IR) energy spectrum. In this paper, scandium oxide (Sc ₂O ₃)-based MIM diodes were fabricated using magnetron sputtering and their rectification performance compared to state-of-the-art Au/Al ₂O ₃/Au diodes. The fabricated Al/Sc ₂O ₃/Al diode has exhibited around two orders of magnitude lower zero-bias dynamic resistance (R _D0 = 956 kΩ) and high zero-bias responsivity (β ₀ = 1 A/W) in advance to Au/Al ₂O ₃/Au diode. The results point to applicability of scandium oxide in MIM rectifiers for IR rectenna.