Kinetic instability of semiconductor alloys

Iya P. Ipatova

, Vladislav G. Malyshkin, and Vitaly A. Shchukin

   Semiconductor alloy epitaxial films grown in immiscibility region de monstrate at some temperatures and compositions the tendency to decompose into the periodic composition modulated structures (supertlattices). Modulated structures occur in the process of the film growth in open system.
   We suggest a concept of semiconductor alloy decomposition due to a kinetic phase transition from the growth regime of the homogeneous alloy to the growth of the composition modulated structure.
   Kinetic instability is promoted by the drift of adatoms in the field of an elastic driving force created according to Vegard's rule by the "frozen" fluctuations of composition in already completed thickness of the film.
   For particular growth mechanism, we focus on the step flow growth of the film from the vapour on the vicinal to [001] surface of cubic substrate. Temperature of decomposition is shown to increase with the increase of elastic effects. The elastic anisotropy is taken into account. The in-plane wave vectors of the most unstable mode of composition fluctuations differ from elastically soft directions. It opens a possibility for formation of superlattices oriented in arbitrary directions.
   Room temperature lasing in laser diodes on the base of modulated structure of InGaAsP alloy has been achieved by I.S. Tarasov from Ioffe Institute RAS.

PACS: 81.15.Aa, 68.65.Cd