Suppressing Ge diffusion by GaAsSb barriers in molecular beam epitaxy of InGaAs on Ge

We have successfully mitigated the out-diffusion of Ge during molecular beam epitaxy of InGaAs on Ge by using a GaAsSb barrier layer as evidenced by secondary ion mass spectroscopy. Compared to GaAs, this GaAsSb barrier layer also results in a smoother surface morphology with its root-mean-square roughness of 0.7nm due to the surfactant effect of Sb. Using a step-graded GaAsSb and AlGaAsSb metamorphic buffer layer, a 200-nm p-type In0.53Ga0.47As layer grown on Ge exhibits a hole mobility of 38cm(2)V(-1)s(-1) with a hole concentration of 2.6x10(19)cm(-3) at 300K and 53cm(2)V(-1)s(-1) with a hole concentration of 1.2x10(19)cm(-3) at 77K.