Deep levels arising from inadvertent defect centers have been studied in both liquid‐encapsulated‐Czochralski (LEC) and liquid‐phase‐epitaxial (LPE)n‐type GaP by using Schottky barrier photocapacitance. In LEC material the total concentration of deep levels in the upper half of the band gap is determined to be about 5×1016cm−3; in LPE material, about 5×1014cm−3. In the lower half of the band gap, optical emission of majority carriers and thermal emission of minority carriers are observed from two distinct levels at 0.4 and 0.1 eV above the valence band edge. These levels are found to have similar concentrations of about 1×1016cm−3in both LPE and LEC material.