Supersaturation in nucleus and spiral growth of GaN in metal organic vapor phase epitaxy

Nucleus and spiral growth mechanisms of GaN were experimentally studied by varying the degree of supersaturation, σ, in selective-area metal organic vapor phase epitaxy. The spiral growth rate of GaN increased proportionally to σ2 in the σ range from 0.0632 to 0.230. The nucleus growth rate of GaN was much smaller than the spiral one in the σ range. The nucleation rate was almost zero at σ lower than 0.130, suddenly increased at higher σ values, and reached ∼107 cm−2 s−1 at σ of 0.230. These results are consistent with a theoretical analysis [W. K. Burton, N. Cabrera, and F. C. Frank, Philos. Trans. R. Soc. London, Ser. A 243, 299 (1951)].