High-quality p+ n Ge diodes selectively grown on Si with a sub-300nm transition region

Selective epitaxial growth of crystalline Ge on Si in a standard ASM Epsilon 2000 CVD reactor is investigated for the fabrication of Ge ultrashallow junction p⁺ n diodes. At the deposition temperature of 700°C, most of the lattice mismatch-defects are trapped within first 300nm of Ge growth and good quality single crystal Ge is achieved within a layer thickness of approximately 1 μm on window sizes up to hundreds of μm². For p⁺ n junction fabrication, a sequence of pure-Ga and then pure-B depositions are utilized for the ultrashallow p-doping of As-doped Ge-islands. The I-V characterization of the diodes confirms the good quality of the Ge and ideality factors of ~ 1.1 with low saturation currents are reliably achieved.