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Heterojunctions, semiconductor structures where two dissimilar materials are joined, were the focus of Zhores Alferov's research. His groundbreaking work in this field revolutionized optoelectronics, enabling the development of highly efficient light-emitting diodes, semiconductor lasers, and solar cells. These advancements have had a profound impact on various technologies, including fiber-optic communications, high-speed computing, and clean energy solutions.