SB-SURFACE SEGREGATION AND THE CONTROL OF COMPOSITIONAL ABRUPTNESS ATTHE GAASSB GAAS INTERFACE/

Quantitative measurements of Sb surface segregation in pseudomorphic G aAs0.8Sb0.2 layers gown on GaAs (0 0 1) using molecular beam epitaxy ( MBE) were performed in situ using the line-of-sight mass spectrometry (MS) technique. It was observed that substantial surface accumulation of Sb occurs under normal growth conditions, giving rise to compositio nal broadening of the GaAsSb on GaAs interface. This compositional gra ding is found to strongly depend on the growth temperature as well as the presence of Sb at the GaAs film surface prior to the initiation of GaAsSb layer growth, We report the effect to substrate temperature an d shutter sequence on the evolution of Sb surface accumulation near th e interface and demonstrate that a compositionally abrupt interface ca n be formed by populating the GaAs surface with an amount of Sb equiva lent to that expected on the GaAsSb surface during growth at steady st ate, Additionally, compositional abruptness at the GaAs on GaAsSb inte rface can be achieved by a ''chemical flashoff'' of the surface Sb pop ulation during exposure to an incident As-2 flux.