Engineers grow nanolasers on silicon, paving way for on-chip photonics

Tony Austin
Monday, 14 February 2011 18:39

Engineers at the University of California, Berkeley, have found a way to grow nanolasers directly onto a silicon surface, which could lead to a new class of faster, more efficient microprocessors, as well as to powerful biochemical sensors that use optoelectronic chips.

'Our results impact a broad spectrum of scientific fields, including materials science, transistor technology, laser science, optoelectronics and optical physics,' said the study's principal investigator, Connie Chang-Hasnain, UC Berkeley professor of electrical engineering and computer sciences.

The increasing performance demands of electronics have sent researchers in search of better ways to harness the inherent ability of light particles to carry far more data than electrical signals can. Optical interconnects are seen as a solution to overcoming the communications bottleneck within and between computer chips.

Because silicon, the material that forms the foundation of modern electronics, is extremely deficient at generating light, engineers have turned to another class of materials known as III-V (pronounced 'three-five') semiconductors to create light-based components such as light-emitting diodes (LEDs) and lasers.

But the researchers pointed out that marrying III-V with silicon to create a single optoelectronic chip has been problematic.

For one, the atomic structures of the two materials are mismatched. 'Growing III-V semiconductor films on silicon is like forcing two incongruent puzzle pieces together,' said study lead author Roger Chen, a UC Berkeley graduate student in electrical engineering and computer sciences. 'It can be done, but the material gets damaged in the process.'

The unique structure of the nanopillars grown by UC Berkeley researchers strongly confines light in a tiny volume to enable subwavelength nanolasers.

Images on the left and top right show simulated electric field intensities that describe how light circulates helically inside the nanopillars. On the bottom right is an experimental camera image of laser light from a single nanolaser.

Images courtesy Connie Chang-Hasnain Group (CCH).

The manufacturing industry is set up for the production of silicon-based materials, so for practical reasons, the goal has been to integrate the fabrication of III-V devices into the existing infrastructure, the researchers said.

'Today's massive silicon electronics infrastructure is extremely difficult to change for both economic and technological reasons, so compatibility with silicon fabrication is critical,' said Chang-Hasnain. 'One problem is that growth of III-V semiconductors has traditionally involved high temperatures - 700 degrees Celsius or more - that would destroy the electronics. Meanwhile, other integration approaches have not been scalable.'

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