Readers Illuminate Issues of Solid-State Lighting

I applaud the authors’ efforts to present a tutorial and current status of the field of solid-state lighting. However, I feel compelled to point out two omissions. The first is the attribution of credit to only Nick Holonyak and his coauthor ¹ for “the first practical demonstration of LEDs in 1962.” The paper by Holonyak and S. F Bevacqua was on semiconductor lasers and has very little to do with LEDs per se. However, if we allow that paper to be a relevant reference for first LEDs, then we must include reference to three other papers ² published at very nearly the same time as Holonyak and Bevacqua’s, as also being “first” practical demonstrations of LEDs. The article by Bergh and coauthors does not distinguish visible LEDs from infrared LEDs. And to be fair about the history of visible LEDs, we should include Henry Round’s publication ³ in 1907 of visible electroluminescence from SiC, the material of choice for blue LEDs before the appearance of GaN-based green and blue LEDs.

The second problem has to do with the data presented in figure 1 of the article. The data there for AlGaAs/GaAs red LEDs start in the early 1980s. In fact, data for “practical” AlGaAs LEDs started with a 1967 paper, ⁴ which was the first report of practical AlGaAs LEDs in the open literature. This paper also represented the first publication of a practical heterojunction.