Nanoscale Tube Photodetectors for Chip-Level Optical Interconnects Developed
8 May 2014
A nanoscale tube-based optical photodetector, compatible with silicon platform integration, has been developed by a team of researchers from McGill University in Montreal working towards creating practical chip-level optical interconnects.
The microtube photodetector is made by rolling-up an indium arsenide/gallium arsenide quantum dot (QD) nanomembrane, driven by a coherent strain that is intentionally introduced in the QD heterostructures during growth by molecular beam epitaxy. Etching parts of the underlying aluminum arsenide sacrificial layer, the strained QD heterostructure rolls up to form a tubular cavity under strain relaxation.
The new photodetector's silicon integration capability is a significant breakthrough, because silicon is not a suitable material for optical communication due to its large bandgap. Designs that use other semiconductors like germanium and III-V compounds have been ineffective as well. Self-organized QD structures, however, have given scientists a way around this because they are defect-free nanoscale islands spontaneously formed during epitaxial growth when the grown film thickness exceeds a critical value.
The new design also allows separate optimization of the photodetector's efficiency and speed, because in it the light absorption length and carrier transport are along separate directions. The use of a microtube optical cavity can also significantly enhance light absorption at desired wavelengths by coupling to the cavity modes.
According to Professor Zetian Mi, member of the research team, it is expected that this technology will quickly evolve from lab innovation to commercialization. It can be applied not only in optical interconnects, but also in biosensors, energy harvesting, microfluidics and micro and nanoelectromechanical systems.