THEORETICAL CONSIDERATION ON THE METALORGANIC MOLECULAR-BEAM EPITAXY GROWTH-MECHANISM OF III-V SEMICONDUCTORS BY MOLECULAR-ORBITAL CALCULATION

Molecular orbital calculations are carried out using the MNDO-PM3 (Modified Neglect of Diatomic Overlap Parametric Method 3) method to study the adsorption of the tri-alkyl metal molecules on the surface of III-V semiconductors. For preliminary considerations, the potential energies between the group III atom and group V atom in a H3III-VH3 molecule are calculated. The results show that the MNDO-PM3 method is applicable to the In-As-H system. Using the In-As-H cluster model, we consider two kinds of surface geometries, i.e. the group V dimer adsorbed on the group III atoms and the excess group V dimer adsorbed on the same group V atoms, to understand the group V effects. The results suggest that tri-alkyl metal molecules adsorb either dissociatively on a group V dimer or by the donor-acceptor bonding on an excess group V dimer. Based on these results, an adsorption model is proposed to explain the group V effects during the MOMBE (metalorganic molecular beam epitaxy) growth.