Spectroscopy of novel light emitting silicon-based diodes

In this thesis, a working novel silicon light emitting diode is demonstrated. Light emission in silicon has been intensively studied since the 1950s when crystalline silicon was recognized as the dominant material in microelectronics. Although room-temperature emission in silicon has been achieved recently, integration for advanced ultra large scale integration is problematic due to poor external quantum efficiency and manufacturing complexity. With the aim of improving the light emission in silicon, rare-earth deposited silicon and impurity-implanted silicon were studied in this work. Rare-earth erbium has been deposited on crystalline silicon by the laser ablation technique. Sharp, intense room-temperature photoluminescence at 1.54 μm was observed for all annealed samples. The thermal quenching factor measured between 80 K to room temperature is less than 2 which is unseen in the past for crystalline based silicon. However, electroluminescence is only obtainable below 160 K for devices fabricated using the similar concepts. Results from photo luminescence excitation spectroscopy proved that excitation from the silicon band-edge recombination is responsible for the erbium emission. Photoluminescence frequency resolved spectroscopy showed that all the samples exhibited a rather long, temperature independent, luminescence lifetime of 90 ± 10 μs. Another approach is carried out to study the light emission in silicon by ion implantation. Samples were produced by low energy boron implantation with various doses up to 2 x 1015 cm-2 followed by rapid thermal annealing at around 950 deg. C. Strong intrinsic silicon band-edge photoluminescence at ∼1.15 μm was observed. Light-emitting diode was made using similar implant and annealing conditions. At room temperature, sharp intense intrinsic silicon electroluminescence is observed with an efficiency of > 2 x 10-6, measured under a forward biased current of 30 mA. This anomalous luminescence increases with temperature by a factor of ∼3 from 80 K to room temperature. TEM shows numerous dislocation loops of interstitial or vacancy type which are related to this silicon band-edge emission. The silicon band-edge emission is also achieved for arsenic-implanted light-emitting diodes during this research period. (author)