Ultra thin layers of new semiconductor can emit and detect light, can be stacked on top of silicon wafers.
Technology has been pushing edges over the course of time. Our smartphones and laptops are becoming wafer-thin, thanks to companies packing in more transistors in small semiconductor chips. However, we also always look for more speed from our processors and RAMs, which is why there’s a new chipset model rolled out every year that’s faster than before. But we are bound to hit a limit for which we can pack in maximum transistors; what will happen post that? Scientists seemingly have an answer.
We know that there’s nothing faster than light waves in the known universe. Therefore, it seems to be the best and the fastest medium to send signals inside microprocessors. MIT postdoc Ya-Qing Bie, who is joined by Jarillo-Herrero and an interdisciplinary team including Dirk Englund, an associate professor of electrical engineering and computer science at MIT, has found out a new semiconductor material that can be stacked on top of silicon chips. The material is called molybdenum ditelluride. This ultrathin semiconductor belongs to an emerging group of materials known as two-dimensional transition-metal dichalcogenides.
"Researchers have been trying to find materials that are compatible with silicon, in order to bring optoelectronics and optical communication on-chip, but so far this has proven very difficult,” Jarillo-Herrero says. “For example, gallium arsenide is very good for optics, but it cannot be grown on silicon very easily because the two semiconductors are incompatible.” In contrast, the 2-D molybdenum ditelluride can be mechanically attached to any material, Jarillo-Herrero says.
Conventional semiconductor materials tend to leak signals within a microprocessor, slowing down processes over time. Another difficulty with integrating them with silicon is that the materials typically emit light in the visible range, but light at these wavelengths is simply absorbed by silicon. With molybdenum ditelluride, both the issues are addressed. There’s no leakage of the signal to other components, resulting in faster processes. Molybdenum ditelluride also emits light in the infrared range, which is not absorbed by silicon, meaning it can be used for on-chip communication.
However, molybdenum ditelluride emits light at a wavelength of 1.1 micrometres, which is ideal for use in chips for computers but not for use in telecommunications. Telecommunication systems operate using light with a wavelength of 1.3 or 1.5 micrometres. “It would be highly desirable if we could develop a similar material, which could emit and detect light at 1.3 or 1.5 micrometres in wavelength, where telecommunication through optical fibre operates,” Jarillo-Herrero says.