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 0.7 nm due to the surfactant effect of Sb. Using a step-graded GaAsSb and AlGaAsSb metamorphic buffer layer, a 200-nm p-type In_0.53Ga_0.47As layer grown on Ge exhibits a hole mobility of 38 cm² V⁻¹ s⁻¹ with a hole concentration of 2.6 × 10¹⁹ cm⁻³ at 300 K and 53 cm² V⁻¹ s⁻¹ with a hole concentration of 1.2 × 10¹⁹ cm⁻³ at 77 K.