Chemical structure of InP surface in MOVPE studied by surface photo-absorption

Using surface photo-absorption (SPA) spectra, we established a surface phase diagram of P-stabilized (001) InP metalorganic vapor phase epitaxy as a function of substrate temperature and PH₃ partial pressure. At 550°C and PH₃ partial pressure of 10 and 30 Pa, the surface is (2×4)-like whose P dimers have a bond axis parallel to [1¯10]. As the substrate temperature decreases and the PH₃ partial pressure increases, the surface changes to an excess-P surface due to P excessively adsorbing onto (2×4)-like surface without cleaving the P dimer bond. A c(4×4)-like surface was not observed. Furthermore, we found that a suppression of excessive P adsorption is needed to obtain a high quality InP epitaxial layer by minimizing native defects that might form