The current-voltage (I-V) and capacitance voltage (C-V) characteristics of Al/n-GaAs and Al/p-GaAs diodes on GaAs substrate treated by Ru3+ ions are investigated and compared with characteristics of GaAs diodes on GaAs untreated substrates. The diodes does not have to show an ideal behaviour of I-V characteristic with an ideality factor of 1.13 and barrier height of 0.85 eV and 0.6 eV for Al/n-GaAs and Al/p-GaAs diodes respectively. The forward bias saturation current found with a big value (10-10A, 10-12 A) in the Al/n-GaAs (untreated) Schottky diodes compared with Al/n-GaAs (treated) diodes. Contrary the forward bias saturation current found with a small value (10-7 A, 10-6 A) in the Al/p-GaAs (untreated) Schottky diodes compared with Al/p-GaAs (treated) diodes. The energy distribution of interface states was determined from the forward bias I(V) characteristics. The interface states density found large in the Al/GaAs (treated by Ru3+ ions) structure comparing with the Al/GaAs (untreated) structure.