PureGaB p+n Ge diodes grown in large windows to Si with a sub-300Â nm transition region

► Monocrystalline Ge-on-Si is grown in large windows with ∼ 300 nm transition region. ► Growth is at 700 °C in a standard Si/SiGe CVD epi-system with an extra line for TMGa. ► A p+ doped Ge surface is made by deposition of pure Ga followed by pure B (PureGaB). ► PureGaB provides low-ohmic p+ contacting and a barrier layer to Al metallization. ► PureGaB Ge-on-Si p+n diodes are nm-shallow and have uniquely low dark current.