Influence of dislocation density and carbon impurities in i-GaN layer on the performance of Schottky barrier ultraviolet photodetectors

The influences of dislocation density and carbon impurities in i-GaN layer on the performance of Schottky barrier ultraviolet photodetectors are investigated. It is found that an increase in dislocation density leads to a decrease in the responsivity, mainly because that the dislocation defects act as charge traps in GaN which can increase the recombination probability of photo-generated electron-hole pairs. On the other hand, it is shown that high carbon impurity content in the i-GaN layer also causes a decrease of the responsivity, mainly because the fact that the photo-generated carriers can't be effectively collected due to the effect of C-induced deep level centers related to carbon impurities. To fabricate high performance GaN based ultraviolet photodetectors, it is important to reduce dislocation density and keep a relatively low concentration of residual carbon during the material growth.