(1. Institute of Atomic and Molecular Science, Frontier Institute of Science and Technology, Shaanxi University of Science and Technology, Xi’an 710021, China) (2. Key Laboratory of Interface Science and Engineering in Advanced Materials of Ministry of Education, Taiyuan University of Technology, Taiyuan 030024, China)
Based on the low-temperature nucleation technology of AlN and GaN, as well as high-temperature thermal annealing technology, the epitaxial growth of high-quality GaN thin films and the activation of p-GaN acceptor has been realized. Since then, GaN-based optoelectronic devices have a great development. However, there are still some fundamental problems for GaN-based optoelectronic devices. Especially, the internal quantum efficiency of GaN-based LED epitaxially grown on heterogeneous substrates is more than 50% while its dislocation density is as high as 108 cm-2. V-shaped pits in the shape of inverted pyramid are common defects in the epitaxial layer of GaN-based LEDs. There are six side-walls in Vshaped pits, and these side-walls all have the angle of 62° with c-plane. Based on the research results of influence of V-shaped pits on optical and electrical properties of LEDs, the screening dislocation theory induced by sidewall quantum wells (QWs) in V-shaped pits was introduced. Owing to the low In content, the barrier height of sidewall QWs is much higher than that of c-plane QWs. Therefore, a high barrier formed around the threading dislocation, which prevents carriers from being captured by the non-radiative recombination center. Moreover, the formation mechanism, surrounding optical properties of V-shaped pits and its influence on electrical properties of LEDs were also reviewed. Meanwhile, the research on optical and electrical properties of LED controlled by V-shaped pits optimization was discussed.