DLTS and low frequency capacitance measurements were made on Schottky diodes formed on Ion-beam etched (IBE) GaAs surfaces. Ion bombardment causes strong low frequency capacitance dispersion, increasing with ion energy. This is attributed to a thin, heavily damaged region, with a trap density in excess of 1017 per cm3. Such dispersion disappears under weak reverse bias and at reduced temperatures. These and other measurements are consistent with a lumped R-C model having components representing the top damaged layer, the underlying space-charge region, and shunt resistance to the ohmic contact.