In this paper, we compare the performances of two RF Dickson rectifiers realized with two different implementations of diodes in the FDSOI 22 nm process. The comparison is performed to provide a power-efficient rectifier for RF energy harvesting at 915 MHz. The I-V characteristics of a conventional MOS diode and an ultra-low power diode (ULPD) are compared in terms of their leakage current. It is observed in the simulation of a 2-stage RF rectifier that minimizing the leakage current using ULPD improves the power conversion efficiency (PCE) of the RF rectifier. Both rectifiers also utilize back gate polarization (BGP) to boost the output voltages. ULPD achieved a Max PCE of 52 %, whereas conventional MOS diode achieved Max PCE of 47 % at 0dBm input power.