Native surface defects on gallium arsenide are detected by thermally stimulated exoelectron emission measurements. Two emission peaks were identified that were correlated to the AsGaantisite defect. Plasma polymerized polythiophene grown on cleaned gallium arsenide is shown to improve the photoluminescence intensity of gallium arsenide and consequently the exoelectron emission measurements indicated the disappearance of one of the peaks. The results thus confirm the passivation of one of the AsGaantisite defects. The effects are also discussed in view of the low angle x‐ray diffraction spectrum for cleaned and polythiophene treated gallium arsenide. Growth of species involving gallium sulfur and arsenic sulfur were also detected.