Kinetic analysis of surface adsorption layer for InGaAsP-related binary materials using in situ RAS

Kinetic analysis of the surface adsorption layer on GaAs, InAs, InP, and GaP surfaces during metalorganic vapor phase epitaxy (MOVPE) was performed by in situ monitoring of the temporal behavior of surface reconstructions using reflectance anisotropy spectroscopy (RAS). When the flow of group-III sources was switched on/off, the transient RA signal exhibited two time constants t₀ and t₁ in response to the generation/extinction of the adsorption layer. It was considered that t₀, when the supply of group-III sources was started, corresponds to the adsorption of group-III atoms from the gas phase to the adsorption layer, and that t₁, when the supply of group-III sources was terminated, is associated with the incorporation of adsorbed group-III atoms to the crystal. The rate constant of adsorption, 1/t₀, was approximately 2 s^-1 for all surfaces except for GaP. The rate constant of incorporation, 1/t₁, ranged from 0.1 to 10 s^-1. It was found that 1/t₁ for the As-containing materials was faster than that for P-related materials, and 1/t₁ for In-containing materials was faster than that for the Ga-containing materials. For the As-containing materials, 1/t₁ agreed with the incorporation rate constants of adsorbed group-III precursors obtained using the Langmuir-Hinshelwood model by the analysis of selective-area growth (SAG).