Results of investigation of forward and reverse currentvoltage characteristics (CVC) of diodes based on GaAs doped by Cr(GaAs:Cr) and doped by Cr, Fe simultaneously (GaAs:Cr,Fe) are stated. It is shown that reduction of base resistance of diodes based on compensated material lead to transformation of static CVC and to appearance of negative differential resistance (NDR) region on reverse CVC.