"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."
The UC Berkeley researchers overcame this limitation by finding a way to grow nanopillars made of indium gallium arsenide, a III-V material, onto a silicon surface at the relatively cool temperature of 400 degrees Celsius.
"Working at nanoscale levels has enabled us to grow high quality III-V materials at low temperatures such that silicon electronics can retain their functionality," said Chen.
The researchers used metal-organic chemical vapor deposition to grow the nanopillars on the silicon. "This technique is potentially mass manufacturable, since such a system is already used commercially to make thin film solar cells and light emitting diodes," said Chang-Hasnain.
Once the nanopillar was made, the researchers showed that it could generate near infrared laser light a wavelength of about 950 nanometers at room temperature. The hexagonal geometry dictated by the crystal structure of the nanopillars creates a new, efficient, light-trapping optical cavity. Light circulates up and down the structure in a helical fashion and amplifies via this optical feedback mechanism.
The unique approach of growing nanolasers directly onto silicon could lead to highly efficient silicon photonics, the researchers said. They noted that the miniscule dimensions of the nanopillars smaller than one wavelength on each side, in some cases make it possible t
|Contact: Sarah Yang|
University of California - Berkeley