Y. Hiraoka et al., Numerical analysis of crystal growth of an InAs-GaAs binary semiconductor under microgravity conditions, J PHYS D, 33(19), 2000, pp. 2508-2518
We investigate the possibility of growing a uniform binary compound crystal
in space, proposing a new crystal growth method. We develop a numerical ca
lculation method for the growth of binary crystals, in which convection ind
uced by temperature and concentration differences in the solution is taken
into account. How to determine the shape and movement of the solution-cryst
al interface during the crystal growth is clearly explained for binary crys
tals, which is more complicated than for single-component crystals. The bou
ndary fit method is employed to solve this moving boundary phase transition
problem. The calculation method is applied to the crystal growth analysis
of an InAs-GaAs binary semiconductor and the effect of buoyancy convection
induced under microgravity conditions on the crystal growth process is inve
stigated. It is found that the concentration held is disturbed and, as a re
sult, the solution-crystal interface is deformed by buoyancy convection, ev
en when the gravitational acceleration is as low as 10(-6) g, which is supp
osed to be the gravity level in the International Space Station which will
start operation in 2004. It is also found that the direction of the residua
l gravity has a strong effect on the concentration held in the solution and
the crystal growth process. Next, we analyse the influence of g-jitters an
d the Soret effect on the crystal growth process. In fact, it is found that
g-jitters and the Soret effect have little influence on the macroscopic cr
ystal growth process. The dependence of the generation of supercooling in t
he solution on convection is also investigated. It is found that supercooli
ng is not induced by convection if residual gravity is 10-6 g. Finally, we
discuss the possibility of growing high-quality InGaAs crystals of uniform
compositions in space.