Ge-Si based n-type films are synthesized using specially designed hydrides P(SiH3)3, Ge3H8 and Ge4H10 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 Ge4H10 to produce materials with P doping densities varying from 4×1018 to a 3.5×1019 cm-3 threshold. These materials are co-doped with Si concentrations ranging from 3×1019 cm-3 to 3.5%, roughly in proportion with the amount of P(SiH3)3 used in the reactions. The second approach applies an alternative ultra-high vacuum chemical vapor deposition (UHV-CVD) technique and Ge3H8 in place of Ge4H10 to achieve ultra-high carrier concentrations up to ∼6×1019 cm-3. The Si content in this case is minimal - in the 2-6×1019 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(SiH3)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(GeH3)3 precursor. These results confirm P(SiH3)3 as a viable CVD doping source that is practical from a process standpoint and therefore attractive for industrial scale-up.
- GeSi photodetectors
- n-type Ge
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics
- Electrical and Electronic Engineering
- Materials Chemistry