A new generation of high speed, silicon-based information technology has been brought a step closer by researchers in the Department of Electronic and Electrical Engineering at UCL and the London Centre for Nanotechnology. The team's research, published in next week's Nature Photonics journal, provides the first demonstration of an electrically driven, quantum dot laser grown directly on a silicon substrate (Si) with a wavelength (1300-nm) suitable for use in telecommunications.
Silicon is the most widely used material for the fabrication of active devices in electronics. However, the nature of its atomic structure makes it extremely hard to realise an efficient light source in this material.
As the speed and complexity of silicon electronics increases, it is becoming harder to interconnect large information processing systems using conventional copper electrical interconnects. For this reason the field of silicon photonics (the development of optical interconnects for use with silicon electronics) is becoming increasingly important.
The ideal light source for silicon photonics would be a semiconductor laser, for high efficiency, direct interfacing with silicon drive electronics and high-speed data modulation capability. To date, the most promising approach to a light source for silicon photonics has been the use of wafer bonding to join compound semiconductor laser materials from which lasers can be made to a silicon substrate.
Direct growth of compound semiconductor laser material on silicon would be an attractive route to full integration for silicon photonics. However, the large differences in crystal lattice constant between silicon and compound semiconductors cause dislocations in the crystal structure that result in low efficiency and short operating lifetime for semiconductor lasers.
The UCL group has overcome these difficulties by developing special layers which prevent these dislocations from reach
|Contact: Alwyn Seeds|
University College London