The growth mechanism of quantum dots (QDs) and nanopits in GaN-InN-AlN material system for both zinc-blend and wurtzitе structures is theoretically investigated. The continuum elasticity model is used for calculations. The nanostructures energy versus their volume, as well as the critical energy and critical volume versus the QD and wetting layer lattice constants relative mismatch ratio (strain ε), are calculated. It was shown that when the zinc-blend GaN is used as a substrate and when the strain between the wetting layer and a substrate overcomes critical ε*=0.039 value, instead of QDs nucleation, the formation of nanopits becomes energetically preferable. Otherwise, when wurtzitе GaN is used as a substrate the critical strain is equal to ε*=0.01, i.e. almost four times smaller. Miscibility gap analysis for GaInAlN quaternary material system is performed by the Gibbs free energy calculations. It is shown that immiscibility gap strongly depends not only on temperature, but also on crystallographic structure. Presented results can be useful at QDs engineering, as well as at the growth of multicomponent bulk crystals and epitaxial thin films in GaInAlN material system.

Keywords: Quantum Dot; Nanopit; Strain Energy; Gibbs Free Energy; Immiscibility Gap;