Enhanced Si–Ge interdiffusion in high phosphorus-doped germanium on silicon

Abstract

Si-Ge interdiffusion with different P doping configurations was investigated. Significant interdiffusion happened when the Ge layers were doped with P in high 10 18 cm −3 range, which resulted in a SiGe alloy region thicker than 150 nm after defect annealing cycles. With high P doped Ge, Si-Ge interdiffusivity is enhanced by 10-20 times in the x Ge > 0.7 region compared with the control sample without P doping. We attribute this phenomenon to the much faster P transport towards the Ge seeding layers from the Ge side during the Ge layer growth, which increases the negatively charged vacancy concentrations and thus the interdiffusivity due to the Fermi effect in Si-Ge interdiffusion. This work is relevant to Ge-on-Si type device design, especially Ge-on-Si lasers.

Study of Si-Ge interdiffusion with phosphorus doping

“…Our recent study showed that high P doping greatly accelerates Si-Ge interdiffusion due to the Fermi-level effect [18]. Si-Ge interdiffusion can change a Ge layer into a SiGe alloy, which delays the lasing of Ge lasers.…”

Interdiffusion in group IV semiconductor material systems: applications, research methods and discoveries

“…The interdiffusion regions for undoped Ge/Si (UGUS) and P-doped Ge/Si (PGPS) are about 60 and 225 nm thick if we define the interdiffusion region is where 0.02 < xGe < 0.98. If we define the interdiffusion region is where 0.05 < xGe < 0.95, the alloy regions are about 45 and 159 nm thick for UGUS and PGPS respectively, which are significant portions of the Ge films, commonly a few hundred of nanometers, for Ge-on-Si lasers [2]. Fig.…”

Improved thin film quality and photoluminescence of N-doped epitaxial germanium-on-silicon using MOCVD

“…shift on emission (band gap narrowing) shows the differences on dopant concentration between the different samples. Given that there is a linear dependence between the Γ-point bandgap shrinkage and heavy n-doping [29], the band narrowing can be predicted using the dopant concentration given on Table 1 for each of the samples. Using a first order phenomenological model for band gap narrowing and using the values of = 0.013 and Δ = 10 −21 / −3 given for Ge [41], the narrowing was calculated and is summarized on Table 4 below.…”

“…The high thermal budget associated with these steps is not desired, as it drives Si-Ge interdiffusion as well as dopant out-diffusion [27], and thus counteracts the efforts in bandgap engineering. Especially, interdiffusion is enhanced with n-type doping by a factor of 2 to 6 with P doping and 1.5 to 3 times with As doping in low to mid-10 19 cm -3 range [28][29][30].…”