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

Ultrashallow junction Ge-on-Si p ⁺n diodes have been fabricated using an epitaxial growth technique of crystalline Ge on Si substrates in a standard ASM Epsilon 2000 CVD reactor. An As-doped Ge is first deposited selectively at the temperature of 700°C where most of the lattice mismatch-defects are trapped at the interface of Ge and Si and vanish within the first 300 nm of Ge growth. Under this condition, good quality single crystal Ge is grown within a layer thickness of approximately 1 μm on different window sizes up to hundreds of μm ². For p ⁺n junction fabrication, the process is followed in the same reactor with a sequence of pure-Ga and then pure-B depositions, to form an ultrashallow p-doping of As-doped Ge-islands that can be metallized by Al. The term PureGaB is introduced for this technology. The I-V and C-V characterization the diodes confirms the good quality of the ultrashallow junction Ge diodes with ideality factors of less than 1.1 and reliable low saturation currents. The doping levels are shown to be such that the depletion over the diodes falls within the Ge region.