Silicon has been the standard material for semiconductor construction for decades, but that could soon change. While producing ever faster technologies, the physical dimensions of chips have decreased over the years, and engineers have known that they would eventually reach physical limitations in trying to make ever smaller and faster chips based on silicon. “We won’t be able to continue improving silicon by scaling it down for long,” says Tomas Palacios, assistant professor in the Department of Electrical Engineering and Computer Science at MIT. “It’s very difficult to make them a lot smaller.”
Of course silicon isn’t the end-all-be-all of transistor material when it comes to speed. “There are several semiconductor materials that offer better performance than silicon,” Palacios says. “The problem is, even though they allow for very fast transistors, they cannot compete with silicon in terms of integration and scalability.” Companies have spent decades and billions of dollars developing technologies based on silicon, and to make a total jump to another material would be neither practical nor profitable.
Palacios and graduate student Will Chung may have developed a solution to the dilemma. Through their research they have determined that out of all of the transistors that comprise a chip, only 5 to 10 percent are performing the actual computations and need to be as fast as possible. Their solution, one that many have tried without success, combines two different types of material on a single chip. The majority of the transistors are silicon based, while that 5 to 10 percent required for optimal speed are made of a different semiconductor material, such as gallium nitride.
Development of these hybrid chips could benefit numerous technologies and are attractive to a multitude of industries. Thomas Kazior, technical director of Advanced Microelectronics Technology at Raytheon Integrated Defense Systems, says this could “enable a new class of high-performance mixed-signal and digitally controlled RF [radio frequency] circuits for use in a wide range of Department of Defense and commercial applications.” Palacios adds that the development of hybrid chips could lead to more efficient mobile phone manufacturing by integrating the typical four or five separate chips in to a single chip.