Control of In Surface Segregation and Inter-Diffusion in GaAs on InGaP Grown by Metal--Organic Vapor Phase Epitaxy

In order to fabricate abrupt heterointerfaces of the GaAs/InGaP system by metal--organic vapor phase epitaxy (MOVPE), we studied the In atom distribution by X-ray photoelectron spectroscopy (XPS). The systematic XPS depth profile analyses revealed that the InGaP surface contains an excess amount of In atoms owing to surface segregation. The excess In atoms diffuse into the GaAs layer and cause compositional mixing at the interface of GaAs on InGaP. In order to suppress the interdiffusion and surface segregation of In atoms into GaAs on InGaP, we have developed a novel gas switching sequence for growing GaAs on InGaP. That is, after the growth of InGaP, only tertiarybutylphosphine (TBP) was introduced, and after stopping the supply of TBP, trimethylgallium (TMGa) was pre-introduced to the reactor before the growth of GaAs. Then tertiarybutylarsine (TBAs) was allowed to flow to initiate GaAs growth. This novel gas switching sequence contributed to the formation of abrupt heterointerfaces of GaAs on InGaP.