When IEEE Medal of Honor winner Nick Holonyak Jr. invented the light-emitting diode in the early 1960s, it would have been difficult to guess that the device would become a mainstay of a global optoelectronics industry worth billions of dollars. Now almost 40 years later, Holonyak and his colleagues Milton Feng and Walid Hafez at the University of Illinois, Urbana-Champaign, have developed a light-emitting transistor or LET, a device that could have an equally profound impact.