A study was made of the evolution of structural defects in AlxGa1–xN films (with x = 0 to 0.6), bombarded with keV heavy ions at 77 or 300K. A combination of Rutherford back-scattering/channeling spectrometry and cross-sectional transmission electron microscopy was used. The results showed that an increase in Al content not only strongly enhances dynamic annealing processes but could also change the main features of the amorphization behavior. In particular, the damage build-up behavior at 300K was essentially similar for all the AlGaN films studied. Ion-beam-produced disorder at 300K accumulated preferentially in the crystal bulk region up to a certain saturation level (~50 to 60% relative disorder). Bombardment at 300K above a critical fluence resulted in a rapid increase in damage from the saturation level up to complete disordering, with a buried amorphous layer nucleating in the crystal bulk. However, at 77K, the saturation effect of lattice disorder in the bulk occurred only for x greater than 0.1. Based upon the analysis of these results for AlGaN and previously reported data for InGaN, physical mechanisms of the susceptibility of group-III nitrides to ion-beam-induced disordering and to the crystalline-to-amorphous phase transition were considered.

Dynamic Annealing in III-Nitrides under Ion Bombardment. S.O.Kucheyev, J.S.Williams, J.Zou, C.Jagadish: Journal of Applied Physics, 2004, 95[6], 3048-54