The pn Junctions of Epitaxial Germanium on Silicon by Solid Phase Doping

Boron and phosphorous layers were deposited by ultrahigh-vacuum chemical vapor deposition at 450 °C using B₂H₆ and PH₃, respectively, to form the abrupt doping profiles in epitaxial Ge on Si substrate. The diffusion process without ion implantation damage is demonstrated by the nearly ideal diode characteristics for the first time. The Ge diodes doped by the boron layer and the phosphorous layer have the ON/OFF ratio of ~1×10⁵ and ~1.5×10⁵ with the extremely low reverse current densities of ~1×10^-4 A/cm² and ~4 × 10^-5 A/cm², respectively. The good crystalline quality at junction free from implantation damage by in situ solid phase doping reflects these figures of merit.