Numerical analysis of crystal growth of an InAs-GaAs binarysemiconductor under microgravity conditions

Abstract

We investigate the possibility of growing a uniform binary compoundcrystal in space, proposing a new crystal growth method. We develop anumerical calculation method for the growth of binary crystals, in whichconvection induced by temperature and concentration differences in thesolution is taken into account. How to determine the shape and movement of thesolution-crystal interface during the crystal growth is clearly explained forbinary crystals, which is more complicated than for single-component crystals.The boundary fit method is employed to solve this moving boundary phasetransition problem. The calculation method is applied to the crystal growthanalysis of an InAs-GaAs binary semiconductor and the effect of buoyancyconvection induced under microgravity conditions on the crystal growth processis investigated. It is found that the concentration field is disturbed and, asa result, the solution-crystal interface is deformed by buoyancy convection,even when the gravitational acceleration is as low as 10-6 g, which issupposed to be the gravity level in the International Space Station which willstart operation in 2004. It is also found that the direction of the residualgravity has a strong effect on the concentration field in the solution and thecrystal growth process. Next, we analyse the influence of g-jitters and theSorét effect on the crystal growth process. In fact, it is found thatg-jitters and the Sorét effect have little influence on the macroscopiccrystal growth process. The dependence of the generation of supercooling inthe solution on convection is also investigated. It is found that supercoolingis not induced by convection if residual gravity is 10-6 g. Finally, wediscuss the possibility of growing high-quality InGaAs crystals of uniformcompositions in space.