Microscopic indium distribution and electron localization in zinc blende InGaN alloys and InGaN/GaN strained quantum wells

Abstract

In order to give an atomic level understanding of the light emission mechanism and seek In distribution patterns closely related to the elusive electron localization centers, we optimize the crystal structure of zinc blende In x Ga1−x N (0≤x≤1) alloys with different In distributions and investigate their electronic structures using first-principles calculations. Our results show that In x Ga1−x N forms a random alloy, in which several-atom In–N clusters and In–N chains can exist stably with a high concentration due to their small formation energy. These In–N clusters and chains form more easily in zinc blende structure than in wurtzite structure. The band gap of zinc blende In x Ga1−x N alloys insensitively depends on the In distribution. Moreover, we find that both small In–N clusters and straight In–N chains with three or more In atoms, acting as radiative recombination centers, highly localize the electrons of the valence band maximum state and dominate the light emission of Ga-rich In x Ga1−x N alloys. The strains of In x Ga1−x N layers can enhance the electron localization in In x Ga1−x N/GaN strained quantum wells. Our results are in good agreement with experiments and other calculations.