Selective Epitaxial Growth of In Situ Doped SiGe on Bulk Ge for p+/n Junction Formation

Epitaxial in situ doped Si0.73Ge0.27 alloys were grown selectively on patterned bulk Ge and bulk Si wafers. Si0.73Ge0.27 layers with a surface roughness of less than 3 nm were demonstrated. Selectively grown p(+)Si(0.73)Ge(0.27) layers exhibited a resistivity of 3.5 m Omega cm at a dopant concentration of 2.5 x 10(19) boron atoms/cm(3). P+/n diodes were fabricated by selectively growing p(+)-Si0.73Ge0.27 on n-doped bulk Ge and n-doped Si wafers, respectively. The geometrical leakage current contribution shifts from the perimeter to the bulk as the diode sizes increase. Extracted near midgap activation energies are similar to p(+)/n Ge junctions formed by ion implantation. This indicates that the reverse leakage current in p(+)/n Ge diodes fabricated with various doping methods, could originate from the same trap-assisted mechanism. Working p(+)/n diodes on Ge bulk substrates displayed a reverse current density as low as 2.2.10(-2) A/cm(2) which was found to be comparable to other literature data. The layers developed in this work can be used as an alternative method to form p(+)/n junctions on Ge substrates, showing comparable junction leakage results to ion implantation approaches.