Dimerization induced incorporation nonlinearities in GaAsP

We find that the incorporation of As and P into GaAs1−yPy, when using gas‐source molecular beam epitaxy, does not depend linearly upon the atomic fluxes within the reactor. Rather, incorporation of As and P into GaAsP goes as the square of the atomic fluxes, i.e., y=fP2/(fP2+βfAs2), where fP(As) is the flux of P(As). β is a fitting parameter and that differs for relaxed and strained GaAsP. The deviation in y from a linear model [y=fP/(fP+fAs)] is as high as a factor of two, whereas our quadratic model is never more than a few percent off. We interpret this as due to surface pairing between two like species (dimerization) in order for them to incorporate into the crystal.