Role of Si and C Impurities in Yellow and Blue Luminescence of Unintentionally and Si-Doped GaN

Both yellow luminescence (YL) and blue luminescence (BL) bands of GaN films have been investigated for decades, but few works report the relationship between them. In this study, two sets of GaN samples grown via metalorganic chemical vapor deposition (MOCVD) were investigated. A close relationship was found between the YL and BL bands for unintentionally doped GaN and Si-doped GaN samples, both of which were grown without intentional acceptor doping. It was found that the intensity ratio of blue luminescence to yellow luminescence (I(BL)/I(YL)) decreases sharply with the increase in carbon impurity concentration, even though both I(BL) and I(YL) increase obviously. It was also found that I(BL)/I(YL) decreases sharply with the increase in Si doping concentration. It is suggested that the C and Si impurities play important role in linkage and competition of the blue and yellow luminescence.