A study was made of a model, for the diffusion mechanism of group-III atoms in an InGaN alloy semiconductor, which used a cell dynamic system approach. In this analysis, attention was focused on gathering information concerning the In-rich region with a dot-like structure that was formed at an early stage in the time evolution of phase separation of this alloy. A similar dot-like structure was known to appear in the active layer of InGaN-based multi quantum-well laser diodes. Thus, the diffusion coefficient of group III atoms in InGaN could be determined by comparing the dot-like structures observed by cross-sectional transmission electron microscopy with those obtained by the cell dynamic system numerical approach. In order to perform this comparison quantitatively, and use it to calculate the diffusion coefficient, a relationship was derived between the rule of mapping used in the cell dynamic system, and the discretization of the Cahn–Hilliard–Cook equation, which described the dynamics of phase separation with a conserved order parameter. The value obtained for the diffusion coefficient was 4 x 10-16cm2/s at a growth temperature of 800C. From this result, it was concluded that the diffusion of group-III atoms arises from atomistic migration on the surface of an InGaN active layer during growth, instead of diffusion within the solid phase.

Diffusion Coefficient of the Order Parameter in the Early Stages of the Time Evolution of InGaN Phase Separation. T.Okumura, Y.Akagi: Journal of Applied Physics, 2001, 90[11], 5515-21