Instability of 'slow' solid-liquid interface relaxation before the hetero-LPE of III-V compounds

Results of specially designed experiments supplemented by numerous literature examples have been analysed in attempt to elucidate the processes occuring at the interface between saturated multicomponent liquid and a non-equilibrium solid before the hetero-LPE of nearly lattice-matched III-V compounds. The 'slow' interface relaxation which provides the moving of non-equilibrium solid-liquid system in the direction of thermodynamic eqilibrium by solid-state diffusion (and which was previously believed to be the only way of equilibrium approach in lattice-matched systems) looses the stability in some cases, being replaced by 'fast' relaxation. It has been shown that the liquid-solid interface instability develops due to a collective action of several factors, and their particular combination produces definite mode of relaxation. The 'slow' relaxation would be unstable, if, as a result of underlying solid dissolution: (I) the lattice parameter of equilibrium solid decreases continuously with respect to that of the substrate, increasing thereby the driving force for dissolution; (II) the solubility of group V component in a changed liquid increases. In a majority of cases the switching to 'fast' relaxation is facilitated by (III) the initial negative difference between the lattice parameters of equilibrium and underlying solids at the growth temperature. (author)