Silicon is the leading material concerning high-density electronic functionality. Integration and economy of scale are the two keys ingredients for the silicon technological success. The present interconnection degree is sufficient to cause interconnect propagation delays, overheating and information latency between single devices. The overcome of this Interconnection bottleneck is together the main motivation and opportunity for the present-day silicon microphotonics, where attempts to combine photonic and electronic components on a single Si chip or wafer are strongly pursued. The main limitation of this technology when is implemented in silicon is the lack of any practical silicon light sources: either an efficient LEDs or a Si lasers.
Despite of all, during these last 10 years many different strategies have been employed to overcome these materials limitations and silicon light emitting diodes (LED) are now only a factor of ten out of the severe market requirements. The main future challenge for silicon microphotonics is the demonstration of a silicon-based laser action to engineer a silicon laser. During the nineties many research efforts have been focused to this goal. A steady improvement in silicon LED performances has been achieved. However it was only at the end of 2000 and during 2001 that many breakthroughs have been demonstrated showing that this field is very active and still promising.
The up to now principal approaches can be subdivided into the following categories:
1. Bulk silicon with extremely high non-radiative lifetime
2. Silicon nanocrystals
3. Doping of silicon with rare earths ions
4. Direct band-gap group IV alloys and quantum confined Si or Ge or group IV alloy structures
5. Quantum cascade Si/Ge structures
During the presentation a critical review of all these approaches will be performed and the most suitable candidate will be underlined.