Growth Mechanism of InP Nanostructure Arrays by Self-Catalyzed Selective Area Epitaxy: A Deep Understanding of Thermodynamic and Kinetic Theories

Nanostructure (NS) growth takes place from a thermodynamic dominant nucleation stage to a kinetic dominant equilibrium crystal state. Although the NS morphology evolution is predictive under the thermodynamic approach, this process has never been explored by kinetics. It has always been unclear how the diffusion-induced growth works during the initial unstable nucleation stage. For a better understanding of these correlated mechanisms, highly uniform arrays of wurtzite InP NSs of ring-like and membrane geometries, grown by self-catalyzed selective area epitaxy, were utilized for theoretical analysis. We found that the driving force of the NS growth is the combined effect of thermodynamic and kinetic mechanisms; they interact with each other during the whole shape evolution process. The concept of "Uniform Diffusion"effect for sidewall growth with different orientations is proposed. Thus, the previous explanation of shape transformation due to minimum energy cost could also be understood in a kinetic way. Based on the above analysis, a general time-dependent growth model of self-catalyzed NSs in arbitrary shape is obtained under the restriction of the thermodynamic approach. Finally, the formation mechanism of trenches on nanomembrane top facets is analyzed.