Measurements on transient capacitance and thermally stimulated capacitance of N-type GaAs epitaxial materials have been carried out. Electron traps could not be detected in LPE materials. However, two electron traps 0.82 and 0.43 eV below the conduction band have been discovered in VPE materials, the electron capture sections are found to be about 2.0×10-13 and 1.5×10-15cm2 respectively.