Clarifying the origin of near-infrared electroluminescence peaksfor nanocrystalline germanium in metal-insulator-silicon structures

2004 
The origin of room-temperature near-infrared electroluminescence (EL) of nanocrystalline germanium (Ge) embedded in oxide was investigated. The nanocrystals were synthesized by partial oxidation of silicon-germanium, Si0.54Ge0.46, films. Under constant current density bias in accumulation and inversion, Ge nanocrystals with diameters of 5 and 10nm exhibit strong luminescence at 1350nm. The 1350nm EL peak is only observed in the presence of elemental Ge and is enhanced with the formation of Ge nanocrystals. The introduction of hydrogen during annealing passivates the dangling bonds at the interfaces of nanocrystals, thus minimizing the energy spread in the 1350nm peak. The 1350nm peak intensity is a function of the injected carrier density, while the peak location remains constant in energy and independent of the applied bias. The results are a clear indication that the luminescence peak originates from radiative recombination of excitons confined in the nanocrystals.
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