UHV-investigation on MOCVD-grown InP(100) surfaces

Epitaxial InP(100)-films were prepared with TBP (tertiarybutylphosphine) and TMIn (trimethylindium) as precursors in a commercial MOCVD reactor. During growth, the V-III-ratio and TBP partial pressure were varied between 50 and 1 and possible changes of the surface structure monitored with the corresponding RAS (reflectance anisotropy spectroscopy) signal based on a correlation established with corresponding LEED measurements. Bulk properties of these films were investigated ex-situ with photoluminescence at 2 K, showing no noticeable difference between the samples. The MOCVD apparatus was modified to facilitate transfer of the sample from the MOCVD environment to UHV in less than 20 seconds (to the 10(-9) mbar range). After transfer, the same RA spectrum was recovered also in the critical case of the P-rich, as-grown surface. A corresponding Auger electron spectrum (AES) did not show any trace of contamination. Furthermore, the surface structure was investigated with LEED and STM. The LEED picture shows a clear (2x1)-pattern with a weak twofold symmetry along the [011] direction, STM pictures revealed a disordered surface terminated by P-dimers.