We study nucleation and evolution of liquid droplets in semi-insulating solid gallium arsenide (GaAs). For a realistic modelling, the crucial issue of a combined thermodynamic and kinetic treatment is the coupling of diffusion, chemical reactions and interface motion with local inhomogeneous mechanical stress fields in the solid matrix. In this note we present a hierarchy of models on various space scales. With more detail we discuss a kinetic model for the Becker-Doring regime and a thermodynamic model to describe diffusion in the vicinity of a single droplet. (C) 2007 Elsevier B.V. All rights reserved.