Investigation of dislocations and defects in epitaxial lateral overgrown GaN by photoelectrochemical wet etching

We introduce a method based on photoelectrochemical (PEC) wet etching that can conveniently investigate the defects and dislocations in laterally overgrown GaN layers by scanning electron microscopy (SEM). The image of SEM illustrates that the dislocation density in homoepitaxial growth region is much higher than in the laterally overgrown region. Also from the SEM image, we can directly identify the region with high density of defects from the perfect region. It is confirmed that the quality of GaN is greatly improved by the epitaxial lateral overgrowth (ELO) technique. The concentration of KOH solution has an effect on etching; when KOH is below 0.02 M, the photo-current increases rapidly according to KOH. After that point, it tents to remain stable at the maximum value of 55 μA. In addition, we find that the photo-current gradually decreases if the etch time is extended. It is probably because more dislocations and defects are revealed.