Role of trapezoidal defects in enhancing the yellow luminescence of high-Al content n-type AlGaN films

Abstract

We have studied the origin of the yellow luminescence of high-Al content n-type AlGaN films. We found that the intensity of the yellow luminescence (YL) band was closely related to the Al/Ga vacancy defects and Si doping, suggesting that the enhancement of the YL band in n-type AlGaN should be ascribed to the donor–acceptor pair transitions from donor impurities such as Si doping to Al/Ga vacancy acceptors in n-type AlGaN films. It is found that the trapezoidal defects formed during the epitaxial growth process may produce a lot of Ga/Al vacancy defects, thus enhancing the yellow band luminescence. By increasing the pressure of the AlN nucleation layer, the formation of trapezoidal defects can be suppressed.