Correlation between luminescent properties and structure organization in AlGaN/GaN superlattices annealed after erbium ion implantation

摘要

The evolution of the structure organization of MOCVD-grown AlGaN/GaN superlattices subjected to erbium ion implantation with an energy of 1 MeV and dose of 3 x 10(15) cm(-2) and subsequent annealing is correlated with their photoluminescent properties. The structure organization is quantitatively estimated using parameter Delta (degree of violation of local symmetry), which is found via multifractal analysis of surface morphology patterns obtained with atomic force microscopy. It is shown that the implantation not only causes Ga segregation on the surface, but also changes the structure organization, which shows up in the finer grain structure compared with the starting one and disordering, as well as in an increase in Delta. As the annealing temperature rises from 700 to 800 degrees C, Delta declines, indicating that the structure organization is improved, and the intensity of the dominating photoluminescence peak due to Er3+ ions (1.542 mu m) grows. With a further increase in the annealing temperature to 1050 degrees C, the structure organization degrades, domains get larger, voids 100-200 nm deep form, and the photoluminescence intensity drops. The formation of voids during high-temperature annealing is also substantiated by data for 230-keV proton scattering. It is thus established that the improvement of the superlattice structure organization activates erbium and causes the erbium-ion-related luminescence intensity to grow.