Optimization of Light emission from Silicon nanocrystals grown by PECVD

Light emission from Si nanocrystals (SiNCs) embedded in Si oxide was studied in this work. SiNCs were fabricated by annealing a Si-rich oxide (SRO) deposited by a plasma-enhanced chemical vapor deposition (PECVD) system, using SiH4 and N2O as precursor gases. The highest photoluminescence (PL) intensity was obtained with a N2O flow rate of 125 sccm, a SiH4 flow rate of 1400 sccm, and annealing temperature of 900 °C. The PL wavelength was controlled by a N2O flow rate and annealing temperature, with blue shifting to the visible wavelengths for increasing N2O flow rate and decreasing annealing temperature. To approach emission at shorter wavelength, a Si oxide with SiNCs / SiO2 multi layer structure (MLS) was fabricated by similar methods. The SiO 2 layer was used as a diffusion barrier to excess Si on vertical direction during the annealing process. Such a barrier can effectively reduce the diameter of SiNCs and shift the emission peak to shorter wavelength. A blue shift in PL was clearly observed as the thickness of Si oxide layer with SiNCs in MLS was reduced. Finally, the light emitting diode (LED) which consisted of n-type poly-Si / Si oxide with SiNCs / p-type poly-Si structure was also fabricated to study the electroluminescence (EL) of SiNCs. The current under the forward bias was about 10 times higher than under the reverse bias. The EL was obtained under a forward bias voltage and the EL intensity was proportional to the current. © 2010 Materials Research Society.

Duke Scholars

Author Yiyang Gong Biomedical Engineering