Germanium partitioning in silicon during rapid solidification

Abstract

Pulsed laser melting experiments were performed on GexSi1−x alloys (x≤0.10) with regrowth velocities ranging from 0.25 to 3.9 m/s. Analysis of post-solidification Ge concentration profiles, along with time-resolved melt depth measurements, allowed determination of the liquid-phase diffusivity Dl for Ge in Si and the dependence of the Ge partition coefficient k on interface velocity v. A Dl of 2.5×10−4 cm2/s was measured. The k vs v data were analyzed using various models for partitioning, including both the dilute and nondilute Continuous Growth Models (CGM). Extrapolating to zero velocity using the partitioning models, an equilibrium partition coefficient of approximately 0.45 was obtained. Best fitting of partitioning data to the nondilute CGM yields a diffusive speed of 2.5 m/s. These measurements quantify previous indications of partitioning observed in other studies of pulsed laser processed GexSi1−x alloys.

Stoichiometry issues in pulsed-laser deposition of alloys grown from multicomponent targets

“…It is well known that upon melting and solidifying Ge will segregate to the surface of Si [12]. This enrichment was previously observed in the SiGe system [4], and we observe it in our RBS analysis of the target after laser irradiation.…”

“…We have modeled this using an analysis similar to that for solute trapping during laser resolidification of alloys [12,13] with the additional feature of removing material from the upper layers of the simulation target. Surface segregation produces an initially large maximum Ge composition in the topmost layers followed by a decay in maximum composition for subsequent iterations until the steady state is reached [14].…”

Characterization of a Czochralski grown silicon crystal doped with 1020 cm‐3 germanium

“…For the Ge-doped Si growth, δ is determined by the diffusivity of Ge ~2.5×10 -4 cm 2 /s [14], the kinematic viscosity v ~2.77×10 -3 cm 2 /s [15] and the crystal rotation rate ω ~0.25 r/s. This results in an equilibrium segregation coefficient k 0 of Ge in Si of about 0.4.…”

Laser‐induced self organization of silicon–germanium hillocks for field emission displays

“…The solidification behavior of Si under laser crystallization conditions is considered to be well understood [1,2]. Incorporating Ge into the Si, however, gives rise to new effects such as segregation [3,4] and growth instabilities. These effects stand behind the appearance of a self-organized hillock structure on the surface of the SiGe samples.…”