Room-temperature Transistor Laser Is Step Closer To Commercialization

"We have shown that the transistor laser, even in its early state ofdevelopment, is capable of room-temperature operation at a speed of 3gigahertz," said Nick Holonyak Jr., a John Bardeen Chair Professor ofElectrical and Computer Engineering and Physics at Illinois. "We expectthe device will operate at much higher speeds when it is more fullydeveloped, as well as play an important role in electronic-photonicintegrated circuits."

Room-temperature transistor lasers "could facilitate faster signalprocessing, large capacity seamless communications, and higherperformance electrical and optical integrated circuits," said MiltonFeng, the Holonyak Chair Professor of Electrical and ComputerEngineering at Illinois. Feng's research on heterojunction bipolartransistors has produced the world's fastest bipolar transistor, adevice that operates at a frequency of 600 gigahertz or more, and is anatural platform on which to develop a transistor laser.

The Illinois researchers first reported the demonstration of alight-emitting transistor in the Jan. 5, 2004, issue of Applied PhysicsLetters. They described the first laser operation of the light-emittingtransistor in the Nov. 15, 2004, issue of the same journal. At thattime, the transistor laser had to be chilled with liquid nitrogen tominus 73 degrees Celsius.

Room-temperature operation is ultimately required for large-scalecommercial applications, said Holonyak, who also is a professor in theuniversity's Center for Advanced Study, one of the highest forms ofcampus recognition. "If this device operated only at low temperature,nobody would want it, except as a laboratory curiosity or for verylimited applications."

After the demonstration of the first semiconductor laser (as well asthe first practical light-emitting diode) in 1962, "it took the effortof many people eight years to get the diode laser to operate at roomtemperature," Holonyak said. "Then it took an additional two years tomake it reliable. But the big payoff has only now just begun, aftermore than 40 years of additional work."

In comparison, it has taken the Illinois researchers less than a yearto move the transistor laser from cold operation to room-temperatureoperation. "Who knows where this new transistor laser technology willbe in another 40 years," Holonyak said. "The payoff part of scientificand technological advances never occurs rapidly, at least not the 'bigpayoff.'

"The transistor laser is still a primitive, laboratory device that willrequire a lot more work," Holonyak said. "Eventually, optimizing thedesign and fabrication will result in higher speed laser operation andimproved performance, as well as a naturally advantageous way torealize electronic-photonic integrated circuits."

Co-authors of the paper with Feng and Holonyak are postdoctoralresearch associates Gabriel Walter and Richard Chan. The DefenseAdvanced Research Projects Agency funded the work.