Al/GaAs Schottky barrier contacts are fabricated with different Ce doping concentrations in the last 100 Å of GaAs before the metal/GaAs interface. Both n- and p-type Schottky barrier heights (SBHs) are measured by current-voltage and capacitance-voltage methods. The n-type SBH is found to decrease with the increasing Ce doping concentration, and the p-type SBH is found to increase to a lesser degree. These SBH changes are considered to be due to energy gap narrowing at the GaAs surface caused by high Ce doping.