Intensity /a.u. The XP survey scan of the as-grown P-rich InP(001) surface reveals a very clean surface only showing emissions from In and P (Fig. ). Especially, no traces of oxygen nor carbon can be found at binding energy BE(O 1s) ≈ 530 eV and BE(C 1s) ≈ 285 eV. The In 3d 5/2 emission is located at 444.25 eV and can be fitted with a single Voigt line, indicating a homogeneous compound surface with no oxidized or segregated subspecies. The associated P 2p emission clearly contains a surface component which appears about 0.51 eV towards higher binding energies than the bulk-related emission at 128.45 eV with a relative intensity of ≈ 9%. We attribute this surface component to P dimers at the reconstructed surface . Surface core level shifts as measured in high resolution synchrotron induced photoelectron spectroscopy are not resolved due to their low binding energy shifts ≤ 0.3 eV . Furthermore, the low energy electron diffraction (LEED) patterns clearly reveal a 2×1 surface reconstruction, where the first order spots are separated by diffuse streaks along the [110] direction (Fig. ). The stabilization of buckled P dimers with atomic hydrogen can be arranged in-phase, resulting in a p(2×2) unit cell or out-of-phase corresponding to a c(4×2) unit cell . The superposition of both unit cells leads to the 2×1-like LEED pattern with the characteristic streaks in the ×2 half-order indicating a 2×2-2D-2H (2 buckled P dimers with 2 atomic hydrogen) surface reconstruction at the present surface as predicted from ab initio calculations . For this very clean and homogeneous surface, the valence band maximum (VBM) is found to be at 0.60 eV, leading to a Fermi level position at the surface located slightly below mid-gap. However, according to the doping concentration of the grown InP with Zinc as shallow acceptor of about N A = 2 • 10 -18 cm -3 , the Fermi level in the bulk is expected to be around 40 meV above the VBM. The discrepancy between measured and calculated Fermi level position relative to the valence band indicates a strong surface band bending of V BB = 0.56 eV due to apparent surface states inducing electrons into the surface which pin the Fermi level as depicted in Figure . Considering a parabolic potential drop inside the InP space charge region (SCR), the amount of total surface charges Q SS can be calculated with Eq. 5, meaning that < 1 % of the surface atoms contribute to a charged defect.