Optimization of the germanium preamorphization conditions for shallow-junction formation

Shallow p⁺-n and n⁺-p junctions were formed in germanium preamorphized Si substrates. Germanium implantation was carried out over the energy range of 50-125 keV and at doses from 3×10¹⁴ to 1×10¹⁵ cm^-2. p ⁺-n junctions were formed by 10-keV boron implantation at a dose of 1×10¹⁵ cm^-2. Arsenic was implanted at 50 keV at a dose of 5×10¹⁵ cm^-2 to form the n⁺-p junctions. Rapid thermal annealing was used for dopant activation and damage removal. Ge, B, and As distribution profiles were measured by secondary ion mass spectroscopy. Rutherford backscattering spectrometry was used to study the dependence of the amorphous layer formation on the energy and dose of germanium ion implantation. Cross-sectional transmission electron microscopy was used to study the residual defects formed due to preamorphization. Complete elimination of the residual end-of-range damage was achieved in samples preamorphized by 50-keV/1×10¹⁵ cm^-2 germanium implantation. Areal and peripheral leakage current densities of the junctions were studied as a function of germanium implantation parameters. The results show that high-quality p⁺-n and n⁺-p junctions can be formed in germanium preamorphized substrates if the preamorphization conditions are optimized