GaP(100) and InP(100) surface structures in the MOVPE ambient

Employing either nitrogen or hydrogen as carrier gas, we investigated the successive development of the characteristic GaP(100) and InP(100) surface reconstructions during thermal induced phosphorus desorption of in the MOVPE reactor. The results differed significantly dependent on the MOVPE ambient, N₂ versus H₂, and the substrate type, GaP(100) versus InP(100). In addition to specifically ordered, well-established P-/H-terminated and cation-terminated surface reconstructions, intermediate surface phases were identified by characteristic RA spectra, when preparing GaP(100) in N2. In contrast, InP(100) showed very similar surface signals independent of the utilized MOVPE process gas. The experimental results were compared to the established surface phase diagrams obtained from first-principles total-energy and electronic structure calculation. For verification of the surface symmetry attributed to the different characteristic in situ RA spectra, the findings were benchmarked with low energy electron diffraction (LEED) measurements after contamination-free transfer of the samples to ultra-high vacuum (UHV). Well-defined, atomically ordered P-rich surfaces are common for MOVPE prepared GaP(100) and InP(100) surfaces, which are terminated by alternating buckled phosphorus dimers stabilized by one hydrogen atom per dimer. Using scanning tunneling microscopy (STM), we resolved individual areas of coexisting p(2×2) and c(4×2) surface symmetry and observed temporal changes of the dimer configurations. Comparison of successive images reveals flipping of the P-dimers in several locations of both GaP(100) and InP(100), which requires shifting of the H-termination between the P-atoms in the respective dimers.