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 0.53 Ga 0.47 As layer grown on Ge exhibits a hole mobility of 38 cm 2  V −1  s −1 with a hole concentration of 2.6 × 10 19  cm −3 at 300 K and 53 cm 2  V −1  s −1 with a hole concentration of 1.2 × 10 19  cm −3 at 77 K.