Threading dislocations related persistent photoconductivity effect in hydride vapor phase epitaxy grown GaN epilayers

Abstract

Deep-level defect-related properties of as-grown and annealed GaN epilayers grown by hydride vapor phase epitaxy (HVPE) are investigated using persistent photoconductivity (PPC) and photoluminescence (PL) measurements. PPC phenomena are seen in these HVPE-GaN epilayers which do not contain the yellow-luminescence (YL) band, suggesting that PPC and YL phenomena are not related. The PPC decay kinetics indicates that the characteristic of the defects which are responsible for the PPC phenomenon would be different from the point defects. The structural qualities of these HVPE-GaN epilayers were characterized by X-ray diffraction. As the densities of threading dislocations decrease, a decrease of photocurrent was clearly observed. The results suggest that the negatively charged threading dislocations are the candidate for PPC effect in our HVPE-GaN epilayers.