Xiaohang Li

No Half Measures: With Semiconductors, the Sky is the Limit.


“I see a lot of myself in the students I interact with.” – Xiaohang Li

Professor Xiaohang Li has his eyes firmly set on the future of humanity. Whether we remain confined to Earth or become a multi-planetary species, one thing is for certain: we’re going to need smaller, cheaper, more-powerful semiconductors, and we’re going to need a lot of them.


“Microchips,” Li proposes, “are arguably the most important foundation of the third and fourth industrial revolutions, as well as the modern life,” and without semiconductors, microchips could not exist. A semiconductor is, as the name suggests, halfway between being an insulator (like ceramic) and a conductor (like copper). The beauty of these devices, according to Li is that “as engineers, we can tune them as we want,” and that’s why they can be found in even the simplest of electronic devices. 


Semiconductors have been around for quite some time now, so much so that Li’s research is focused on “fourth-generation semiconductors,” and his team has made multiple pioneering contributions, such as the first Complementary Metal–Oxide–Semiconductor (CMOS) and the first flash memory.  These new devices with ultrawide bandgap can do things that traditional semiconductors like silicon can’t do, such as withstand extreme temperatures. These properties will be a minimum requirement, Li explains, when the time comes for humanity “to explore the universe as well as the Earth, below the surface.” For a smartwatch to work on Mercury, for example, its semiconductors would need to withstand temperatures, “anywhere from -200 to 400 degrees Celsius,” although thankfully Li remains optimistic that colonizing Mercury will not be necessary.


Li is grateful to be doing this work at KAUST, especially since “it offers faculty a certain amount of resources to freely explore so-called ‘blue-sky problems.’” He describes how researchers at other institutes can be restricted to projects that will have “practical impact in the next couple of years,” yet because of the ample funding and resources available at KAUST, “we can also look at the blue-sky problems that may bear fruit in ten years or fifteen years.” This freedom is what allows Li and his team to flourish, and what propels him through each day’s work; “every morning I can't wait to get up and to work collectively with my students and team so we can realize interesting scientific discoveries and engineering breakthroughs.”


One such discovery has led, after “extensive semiconductor physics study,” to the development of a cloud-based software that is already in use by “researchers from over 70 universities and companies around the world.” Li’s humility inclines him not to brag, but when pressed for details he offers an impressive list of names, including Cambridge University and Meta (which owns Facebook). As much as he wants to be at the cutting edge of more discoveries like this, he knows that the kind of progress he hopes for can only be made with contribution, co-operation and participation from other research institutes and so-called ‘Big Tech’ companies.


The collective work that fueled the success of Li’s software is key to his efforts, and it’s evident that he values his interactions with students as much as with his more-senior colleagues; “I was a Ph.D. student not too long ago,” he says, “and I see a lot of myself in the students I interact with.” Li’s empathy and understanding are crucial ingredients in his approach to his work at KAUST, which he is confident can have a profound impact on the future of technology.


In their pursuit of smaller, cheaper, more-powerful semiconductors, Li and his team are determined to match the pace set by those who have gone before them; “seventy years ago you could hardly pack a few transistors into the space of your fingernail,” he explains, “but right now you’re talking tens of billions of transistors,” within the same dimensions. With all those transistors it might seem like there’s hardly any room for improvement; for many, tens of billions of anything would be more than enough. For Li and his team however, that’s merely where the bar is set, and for them, the challenge is very much accepted.