Influence of the structural inhomogeneity on the luminescent properties of nitride multiple quantum wells grown by MOCVD

Abstract

Abstract. We investigated GaN/InGaN multiple quantum wells grown by MOCVD for LED application in the blue and green regions. The sample considered was characterized by a significant number of defects on the interfaces between the layers. We examined the heterostructure by means of cathodoluminescence. Due to the composition and the layer's thickness fluctuations on a small and a large scale, we observed peak splitting and broadening. In order to justify our assumption, we compared the experimental results with our theoretical calculations. The theoretical model used is based on the T-matrix formalism. IntroductionThe III-nitride layered heterostructures have acquired widespread applications as building blocks in manufacturing of devices for optical communication, high-electron-mobility transistors, ultra-violet lasers and resonant-tunneling-based structures for THz applications [1][2][3]. Along with the attractive characteristics [4], they also possess very specific ones, such as well pronounced piezoelectric and spontaneous polarizations along the low-symmetry axis. These features should always be taken into account when considering thin III-nitride layers, especially in superlattices and multiple quantum wells. The optical properties of such structures are greatly affected by the presence of macroscopic polarization in the layers. Another important factor that influences the optical properties is the interface roughness, which is manifested as wells with fluctuations [5][6][7].In this study, we examined by means of cathodoluminescence an InGaN/GaN multiple quantum well (MQW) grown by MOCVD on a GaN substrate. All measurements were conducted at room temperature. Further, we compared the experimental results with our theoretical calculations based on the model briefly described in [8]. Our main goal was to demonstrate that, despite the idealizations and the simplifications we have made, our calculations are in a satisfactory agreement with the experimental results. We conducted our calculations in the framework of the effective-mass approximation and the T-matrix formalism. To ensure the accuracy desired, the Airy function formalism was used to solve the one-dimensional Schrödinger's equation for the MQW potential.