Ultrafast carrier dynamics in In_xGa_(1-x)N (0001) epilayers: Effects of high fluence excitation

摘要

Ultrafast carrier dynamics in In_xGa_(1-x)N (0001) epilayers were investigated, using femtosecond transient differential transmission and reflection measurements for x = 0.07, 0.15, and 0.33, over a fluence range of 1-12 mJ/cm~2. Stimulated emission as well as band gap renormalization play a crucial role in the dynamics of the photogenerated carriers. Threshold fluence leading to saturation of the differential reflectivity and transmission signals related to the In mole fraction has been observed, which is attributed to band gap renormalization, Auger process, and carrier recombination through In-rich nanoclusters. Furthermore, coherent acoustic phonon oscillations have also been observed in the In_(0.15)Ga_(0.85)N at high fluence excitation.