In the 1980s, all known material systems possessing the necessary properties for blue-light emission had shortcomings, thus negating their utilization in efficient LEDs. Gallium nitride (GaN) was one possible candidate, though, at the time, no p-type or active layer could be created. These challenges were ultimately overcome by Shuji Nakamura, who describes the path to the first blue GaN LED in his Nobel Lecture.
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Shuji Nakamura (2015) studied this question.