Recent advances in processor technology have lead to a bottleneck in communication with memory. Trying to overcome this barrier with the currently used method — smaller, better designed semiconductors — is impractical due to the higher power necessary to transport data at higher rates. Scientists at MIT believe they may have discovered a way to circumvent this limit — the use of germanium lasers.
Researchers at MIT have demonstrated the first germanium laser that can produce wavelengths of light useful for optical communication and is functional at room temperature. The scientists hope to apply this new technology to the world of processors and begin moving data and (possibly) performing calculations using light instead of electricity.
The process of integrating these new components into the chip has the potential to be very expensive, however. Assembly of a chip an extremely difficult process in which materials are layered onto a silicon wafer and patterns are etched into them. Additionally, materials must chemically bond with layers above and below it in a chemical and thermal environment conducive to all the rest of the materials used during assembly.
Traditionally used lasers like gallium arsenide serve as an example of the difficulty of incorporating un-favorable materials; in addition to the fact that it is more expensive than silicon to begin with, the lasers have to be grafted to the semiconductor separately. Fortunately, however, germanium is already being integrated into manufacture processes for its ability to increase chip speed.
From more of a pure research perspective, this work proves an important hypothesis: indirect-band-gap semiconductors can in fact produce practical lasers. This fact comes as a counterpoint to the generally accepted opinion that indirect-band-gap semiconductors will never produce laser light. The formerly accepted opinion comes from the tendency for these types of materials to produce heat rather than light, a tendency that MIT scientists overcame through such methods as doping (adding atoms from another element).
The director at Massachusetts-based Analog Devices Semiconductor offers excellent insight into this new technology, explaining that, “High-speed optical circuits like germanium in general, that’s a good marriage and a good combination. So their laser research is very, very promising.”
Miao continues, pointing out that the germanium lasers need to become more energy-efficient before they can truly be considered a practical source of light for optical communications systems. “But on the other hand,” he says, “the promise is exciting, and the fact that they got germanium to lase at all is very exciting.”
Further reading on the engineering required to accomplish this feat can be found in this letter, which is to be published in the journal Optical Letters.