Optoelectronic properties of GaN epilayers in the region of yellow luminescence

We studied a GaN epitaxial wafer grown by metal organic chemical vapor deposition, in which a lateral variation in the density of dislocations and associated defects was induced by a special preparation of the GaN buffer layer. Electron beam induced current and photocurrent measurements reveal lateral variations in the electrical properties of the GaN epilayer corresponding to the gradient in the defect density. The photocurrent spectra show four well distinct peaks separating the well known defect related yellow band in a blue, a green, a yellow, and a red component. In particular, we observe a strong dependence of the green component on the density of the $a$-type threading dislocations. There is evidence that the green and the yellow components are also significantly influenced by point defects.