An In surface segregation effect during the growth of InGaAs on GaAs by molecularhyphen;beam epitaxy has been studied by reflection highhyphen;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 twohyphen;dimensional to threehyphen;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 modulationhyphen;doped fieldhyphen;effect transistors.
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