Surface potentials in chemically etched n- and p-GaInP2(100) are investigated by synchrotron-radiation photoemission spectroscopy at room and liquid-nitrogen temperatures. It is found that at low temperature the surface band bending in both n- and p-GaInP2(100) is reduced so that the surface bands become nearly flat. This effect is explained in the framework of semiconductor surface electrostatics. The proposed model enables quantitative characterization of the surface state spectrum based on the experimentally determined values of the surface potential at different temperatures. In particular, the surface states density values obtained are 2 × 1012 and 7 × 1012 cm–2 for n- and p-GaInP2(100) surfaces, respectively.