In surface segregation and growth-mode transition during InGaAs growth by molecular-beam epitaxy

An In surface segregation effect during the growth of InGaAs on GaAs by molecular-beam epitaxy has been studied by reflection high-energy electron diffraction measurements supported by a segregation model. Indium atoms segregate at a ratio of more than 0.8 under the conventional growth conditions for InGaAs, which causes the formation of accumulated In atoms on the surface. The transition from two-dimensional to three-dimensional growth occurs when the amount of In reaches around 1.7 monolayer with a nominal alloy composition greater than 0.25. This transition determines the upper limit on the In composition of the InGaAs layer for application as an electron channel in modulation-doped field-effect transistors.