Control of dislocation morphology and lattice distortion in Na-flux GaN crystals

摘要

The dislocation morphology and lattice distortion, including the tilting and twisting of lattice planes, at the Na-flux GaN/seed-GaN interface were investigated using transmission electron microscopy (TEM) and position-dependent nanobeam X-ray diffraction (nanoXRD). The results revealed that the dislocation morphology and lattice distortion in Na-flux GaN at the initial growth stage are strongly influenced by the seed-GaN surface morphology and the growth mode of Na-flux GaN. From the TEM results, one can observe that the formation of dislocation-related etch pits (DREPs) on the seed-GaN surface and the three-dimensional (3D) growth mode for Na-flux GaN give rise to the bending and lateral propagation of dislocations penetrating from the seed-GaN to the Na-flux GaN. This simultaneously results in homogenization of the GaN crystal domain structure as confirmed by nanoXRD. The mechanism responsible for the bending and lateral propagation of dislocations by the formation of DREPs and the 3D growth mode for the Na-flux GaN and the correlation between the dislocation morphology and the lattice distortion are discussed on the basis of TEM and nanoXRD results.