Homoepitaxial InP (001) was grown on p-type InP (001) (Zn doped, 2 -2.3 • 10 18 cm -3 with 2 • miscut toward < 111 > direction) in a horizontal-flow metalorganic vapor phase epitaxy (MOVPE) reactor (Aixtron, AIX-200) modified to enable a contamination-free transfer to UHV using H 2 as carrier gas. Tert-butylphospine (TBP) and trimethylindium (TMIn) were used as precursors. Diethylzinc (DEZn) was used as a p-dopant source for grown InP(001) epilayer. Molar flow of DEZn was adjusted to ensure a carrier concentration of 2 • 10 18 cm -3 in the InP(001) epilayer, which was finally confirmed by electrochemical capacitance voltage profiling. The growth was monitored by reflection anisotropy spectroscopy (RAS) which allows the specific preparation of the P-rich surface (see for details). After sample preparation at TU Ilmenau, the sample was transferred via an UHV transfer shuttle with a base pressure ≤ 5 • 10 -10 [11] to TU Darmstadt.