Non-conventional routes to SiGe:P/Si(100) materials and devices based on -SiH3 and -GeH3 derivatives of phosphorus: synthesis, electrical performance and optical behavior

Ge–Si based n-type films are synthesized using specially designed hydrides P(SiH 3 ) 3 , Ge 3 H 8 and Ge 4 H 10 for potential applications in next-generation CMOS technologies. The films are grown on Ge buffered Si(100) at 340 °C using two complementary methods. The first employs a gas-source molecular epitaxy approach using Ge 4 H 10 to produce materials with P doping densities varying from 4 × 10 18 to a 3.5 × 10 19 cm −3 threshold. These materials are co-doped with Si concentrations ranging from 3 × 10 19 cm −3 to 3.5%, roughly in proportion with the amount of P(SiH 3 ) 3 used in the reactions. The second approach applies an alternative ultra-high vacuum chemical vapor deposition (UHV–CVD) technique and Ge 3 H 8 in place of Ge 4 H 10 to achieve ultra-high carrier concentrations up to ∼6 × 10 19 cm −3 . The Si content in this case is minimal—in the 2–6 × 10 19 cm −3 range—indicating that the growth mechanism allows only 'impurity' levels of Si to be incorporated. The active carrier densities in both cases closely reflect the absolute P content, indicating that the P atoms are mostly substitutional. The electron mobilities are significantly higher compared to state-of-the-art prototypes, probably due to superior microstructure and dearth of inactive donors in the lattice. P–I–N diodes fabricated using the P(SiH 3 ) 3 compound show I – V characteristics comparable to state-of-the-art results for Ge-on-Si devices and are virtually undistinguishable from similar diodes doped with the P(GeH 3 ) 3 precursor. These results confirm P(SiH 3 ) 3 as a viable CVD doping source that is practical from a process standpoint and therefore attractive for industrial scale-up.