Effects of fixed charge on R(0)A value of ZnS-passivated x = 0.3 HgCdTe n-on-p diode are explained as a shunt resistance that affects current-voltage (I-V) and dynamic resistance-voltage (Rd-V) characteristics. The fixed charge of 1 x 10(11)/cm(2) to 2 x 10(11)/cm(2) which is usually obtained with ZnS passivation makes the surface weakly inverted and reduces HgCdTe diode R(0)A value owing to the short generation lifetime of HgCdTe substrate. The gate-controlled diode and specially fabricated diode are used to explain the surface leakage cur rent in the weak inversion and charge sheet model is used to explain the characteristics. It is found that the surface leakage current by the inverted channel in the weak inversion can reduce R(0)A more than other currents such as the generation current and tunneling current which are usually used to explain the surface leakage current of HgCdTe diode.