Chemical Segregation in Vertical Bridgman Growth of GaInSb Alloys

Abstract

Cryst. Res. Technol. 34 1999 4 449-456 A set of experiments on the solidification of Ga 1-x In x Sb alloys with a large variation of the sample diameter (from 1mm to 10mm), of the growth rate (from 0.7 to 7 µm/s) and of the concentration (from x=0.01 to x= 0.1) is described. The associated radial and longitudinal segregation of the In have been analysed by SIMS or electron microprobe. Numerical simulation of the experiments, taking into account thermal, hydrodynamic and chemical behaviour has been carried out with the help of FIDAP. It is shown from these numerical results that a plateau of concentration can be reached even if a convective loop is present close to the interface, provided that the convection does not extend into the bulk of the liquid. This is in full agreement with the experimental results obtained. Supporting this analysis, in some experiments, a defect in term of verticality of the crucible led to complex 3-D convection involving the whole liquid, and in that case no plateau was obtained.For the radial segregation ∆C R , three regimes of transport are found, characterised by the convective level:-A diffusive one, with a low, constant, ∆C R related to the interface curvature.-A quasi-diffusive one (weak convection) in which ∆C R increases with convection. -A convective one in which it decreases. Measured radial segregations are in good agreement with predictions from the numerical simulations.

Oscillations of the longitudinal solutal profile in Bridgman growth of doped crystals

“…[7,14]. One experiment about the vertical Bridgman growth of 1% doped crystal has been also numerically analyzed in Ref.…”

One-dimensional model of the equiaxed grain formation in multi-crystalline silicon

“…2D or 3D simulations would allow considering local faceting of the interface. electromagnetic levitation set-up has been developed in order to measure these thermo-physical properties [19]. It is found that the Si undercooling is a function of C concentration [20,21].…”

Industrial challenges for numerical simulation of crystal growth

“…Alloy segregation is a critical issue in the growth of bulk ternary III-V crystals [2]. These materials could provide lattice-matched substrates for epitaxial growth that eliminate the need for a graded bu®er layer and thus reduce the production costs and increase the life-time of semiconductor devices due to the lower density of the mis¯t dislocations.…”

“…The di±culty of growth of such ternary compounds as GaInAs and GaInSb stems from the large solidus-liquidus separation of the phase diagram and thus a small value of the In segregation coe±cient. The rejected solute accumulates at the interface and is transported by di®usion and convection, the latter having a major e®ect on the quality and the composition uniformity of the grown crystals [2,13]. Various defects such as striations or cellular structure in ternary In-containing crystals leading to poly-crystallinity when the solute concentration exceeds a critical value [47] are often observed.…”