As Surface Segregation during the Growth of GaInP on GaAs

We have studied the interface between GaInP and GaAs grown by gas source molecular beam epitaxy using X-ray photoelectron spectroscopy. The presence of As atoms at the phosphide surface is detected, even for an epilayer thickness as large as 5000 Å. We show that this can be explained by the segregation of a small amount of As (∼1%) incorporated during GaInP growth. On the other hand, a large (∼6 monolayers) interface broadening is observed and results mainly from the incorporation of a large amount of As at the interface due to gas mixing during the commutation. Although a large difference in chemical bond strength exists between anions and cations at the interface which could lead to important interdiffusion processes, the reaction between GaAs and GaInP is impeded at 500° C. This implies that, at this temperature, kinetic factors are dominant. Hence, with an optimized gas commutation sequence, it should be possible to grow nearly abrupt interfaces between GaInP and GaAs at 500° C.