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 occurring 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 equilibrium 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: (1) 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.