Improved compositional abruptness at the InGaAs on GaAs interface by presaturation with In during molecular-beam epitaxy

Surface segregation of In atoms during molecular beam epitaxy of InGaAs layers greatly influences the composition profile in the vicinity of both the normal and the inverted Ga(Al)As/InGaAs interface, inherently limiting compositional abruptness. We find, for example, that the intended alloy composition in In0.22Ga0.78As is not reached until nearly 35 Å from the InGaAs on GaAs interface for growth at 500 °C. We propose and demonstrate how the compositionally graded region in InGaAs can be eliminated by preadsorbing a fixed amount of In onto the GaAs surface to match the surface segregated layer during steady state, before depositing the InGaAs layer.