摘要
AIN thick films were grown on c-plane sapphire substrates by hydride vapor phase epitaxy at high temperature. The evolution of the strain state and crystal quality of AIN with increase of thickness were investigated by transmission electron microscopy, field-emission scanning electron microscopy, Raman spectra and atomic force microscopy （AFM）. As the thickness increased, the stress in the epilayers decreased gradually, which was attributed to the reaction of dislocations at the first several microns in thickness. When the thickness was more than 20 μm, the stress was almost fully relaxed due to the formation of cracks. Wet etching experiments indicated that the dislocation density decreased with the increase of thickness. The AFM images showed that the density of dark spots on the surface obviously decreased and the atomic steps became straight as the thickness increased.
AIN thick films were grown on c-plane sapphire substrates by hydride vapor phase epitaxy at high temperature. The evolution of the strain state and crystal quality of AIN with increase of thickness were investigated by transmission electron microscopy, field-emission scanning electron microscopy, Raman spectra and atomic force microscopy （AFM）. As the thickness increased, the stress in the epilayers decreased gradually, which was attributed to the reaction of dislocations at the first several microns in thickness. When the thickness was more than 20 μm, the stress was almost fully relaxed due to the formation of cracks. Wet etching experiments indicated that the dislocation density decreased with the increase of thickness. The AFM images showed that the density of dark spots on the surface obviously decreased and the atomic steps became straight as the thickness increased.
基金
Project supported by the National Basic Research Program of China(No.2012CB619305)
the National Natural Science Foundation of China(Nos.61274127,61474133,61325022)
the CAS Project of Introduction of Outstanding Technical Talent
