Theoretical studies on the chloride ALE process

Ab initio molecular orbital calculations were performed to systematically investigate the chloride atomic layer epitaxy (ALE) process of GaAs. In the Ga layer formation, the GaCl molecule as a source is first adsorbed onto the As dangling-bond (DB) site through electronic “configuration mixing”. Consequently, the ambient H2 reactively eliminates the Cl atom as HCl, where the “electron delocalization” is the driving factor of reaction. As layer formation via As2 adsorption onto the Ga-DB site was also investigated. The results show that the π orbitals of As2 are used to form the As-Ga bonds through “configuration mixing”, as in the case of GaCl/As-DB. The calculated energetics are consistent with the experimental data.