Heavily phosphorus doped germanium with local strain compensation effect by Co-implantation and rapid thermal process

Abstract

This study explored the effects and mechanisms of phosphorus (P), tin (Sn), and yttrium (Y) co-implantation in germanium (Ge). A series of dopant concentration measurements and electrical evaluations showed that the co-implantation process significantly enhanced P concentration in Ge, resulting in heavily doped regions. While P/Sn co-implantation showed limited advantages under low-temperature rapid thermal process (RTP), and P/Y co-implantation proved the effect of local strain compensation, the combined P/Sn/Y co-implantation achieved the highest concentration of P in Ge. At a RTP at 700 °C, we attained the remarkably high peak P concentration of 4.14×1020 atoms/cm3. This represents a 40-fold increase in P concentration compared to the conventional P single implantation method, using complementary metal-oxide semiconductor (CMOS)-compatible processes, and resulted in enhanced contact behavior. Geometric phase analysis (GPA) allowed visualization of the applied strains and stresses among the dopants and Ge atoms at nanometer resolution. The formation of strain-stress clusters by the large atomic radius Y was analyzed using GPA, and found to impact dopant distribution.