Suppressing Ge Diffusion By Gaassb For 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 layer as evidenced by secondary ion mass spectroscopy. Compared to GaAs, this GaAsSb layer also provides a smoother surface morphology with its root mean square roughness of 0.664 nm. Using a GaAsSb step-graded buffer (SGB) and an AlGaAsSb high resistivity buffer, we are able to grow a 200 nm p-type InGaAs layer on Ge and yield hole mobility of 37.5 cm 2 /V-s at 300K and 53.1 cm 2 /V-s at 77K with hole concentration of 2.6×10 19 cm −3 and 1.2×10 19 cm −3 , respectively.