Sb-surface segregation and the control of compositional abruptness at the GaAsSb/GaAs interface

Quantitative measurements of Sb surface segregation in pseudomorphic GaAs0.8Sb0.2 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 compositional broadening of the GaAsSb on GaAs interface. This compositional grading 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 and shutter sequence on the evolution of Sb surface accumulation near the interface and demonstrate that a compositionally abrupt interface can be formed by populating the GaAs surface with an amount of Sb equivalent to that expected on the GaAsSb surface during growth at steady state, Additionally, compositional abruptness at the GaAs on GaAsSb interface can be achieved by a ''chemical flashoff'' of the surface Sb population during exposure to an incident As-2 flux.