Dual-Color Electroluminescence ( $\lambda \approx \hbox {450} \hbox {nm}$ and 650–700 nm) From a Silicon-Based Light Source

In this letter, bright "purple" electroluminescence is observed from a multilayer stack with thin amorphous silicon (alpha-Si)/SiO₂, due to the dual-color light emissions in blue and red. Under photoexcitation, the blue emission is negligible compared with the long wavelength red emission and is only present weakly after anneal in N₂ exceeding 900degC. However, under electrical excitation, the blue becomes obviously visible and shows faster increasing rate with increased carrier injection than the red. From analysis of the samples with different alpha-Si thicknesses (2-7 nm), the red emission is deemed to have resulted from the quantum-confinement effect within the thin alpha-Si layers, whereas the blue emission is speculated to have originated from the Si/SiO₂ interfacial defects.