John Wager is holding one of the original transparent transistors developed in his lab that led to the oxide TFT technology inside the new Apple 5K Retina Display.
John Wager eagerly awaited the arrival of his new computer monitor — not just because it was the newest Retina display from Apple — but because some of the technology inside it was developed in his lab over a decade ago.
“It’s mind boggling!” Wager said of the recent commercialization of technology that was initially a very small fish in a $100 billion industry.
As early as 2003, Wager, holder of the Michael and Judith Gaulke Chair in the School of Electrical Engineering and Computer Science at Oregon State, proposed the use of oxide semiconductors for thin-film-transistors (TFT) in flat-panel displays. They could potentially produce brighter displays at higher resolutions than the standard technology, but industry was not immediately interested. Flat-panel display companies were happy using amorphous silicon for their TFTs and were developing low-temperature polysilicon (LTPS) as a next-generation replacement technology.
But Wager did not give up, and as research advanced it became clear that the amorphous oxide semiconductors his group was working on had advantages over LTPS for some applications. In a nutshell, it was faster at turning on and off an array of transistors — which is what is needed in more advanced flat-panel displays. Using the material, called IGZO (indium gallium zinc oxide), TFTs were cheaper to produce. Current amorphous silicon factories could be retrofitted to use IGZO, whereas LTPS manufacturing would require new factories to be built.
It took several years of development, but Sharp became the first company to start producing flat panels with IGZO and since then all the major display companies have begun testing the waters.
“It is beginning to look like the minnow might just swallow the whale,” Wager said.
Ironically, Wager and his group did not set out to revolutionize flat-panel displays. In a collaborative research project at Oregon State with chemists Art Sleight and Doug Keszler and physicist Janet Tate his group was working on testing new materials for potential use in bipolar transparent electronic applications. The materials they initially pursued were difficult to work with, so Wager turned to conventional transparent conductive oxides that had been used since WWII for applications such as deicers in military planes.
In that class of materials, Wager chose zinc oxide — commonly used as a sunblock — to test first. Graduate student, Randy Hoffman, took on the task of working with the material and stayed over winter break in 2001 to invent the very first transparent transistor. Wager knew right away it would be big and sought out patents for their inventions. Although they eventually moved away from zinc oxide, Hoffman’s invention was the key initial breakthrough.
“None of this would have happened if it wasn’t for Randy. He was really critical,” Wager said. In 2012, Hoffman received the Council of Outstanding Early Career Engineers Award from the College of Engineering at Oregon State.
“The opportunity to actively participate in the development of a new semiconductor device technology from invention in the labs at OSU through commercialization in the flat-panel display industry has been tremendous, and is an exemplary picture of constructive collaboration between academia and industry,” Hoffman said.
Although commercial implementation of transparent electronics will take further development, companies like Corning are excited about possibilities (demonstrated in a conceptual video) such as a bathroom mirror that could show your schedule for the day or an automobile windshield that could display driving directions.
Transparent electronics research allowed Wager’s group to push innovation, and they haven’t stopped there. His lab continues to explore other new materials including amorphous metal thin films with atomically smooth surfaces.
“The unique properties of some of our materials offer new opportunities to do things that people have never been able to do before,” Wager said. An emerging application exhibited by Samsung is a smart window that operates as a touchscreen computer, a TV screen, and electronic blinds that can open and close at the touch of your finger.
Other research involves looking at materials that could improve solar cell technology made from thin films, and new inorganic materials that could lead to large-area, solid-state lighting applications.
“It’s really just a matter of having the imagination to think of what’s possible, and then getting lucky,” Wager said of the potential applications for his innovations in new materials.