Electroluminescence from silicon nanocrystals embedded in silicon oxide and silicon nitride

Abstract

Electroluminescence (EL) from nc-Si embedded in both silicon oxide and silicon nitride matrix was demonstrated. Nc-Si embedded in silicon oxide was formed by depositing silicon rich silicon oxide (SRSO) thin films with electron cyclotron resonance plasma enhanced chemical vapor deposition system and post thermal annealing at high temperature. We found that the luminescence peak wavelength ranged from 750 nm to 900 nm could by controlled by the change of deposition condition and the optimum annealing parameter for nc-Si luminescence was thermal annealing of SRSO film at $1100^{o}C$, for 30 minutes. The origin of the luminescence was attributed to the radiative recombination of electron-hole pairs formed in nc-Si. Light-emitting device (LED) based on SRSO films with various structures was demonstrated and we concluded that the EL from nc-Si embedded in $SiO_{2}$ was mainly originated from the impact excitation via hot carriers. Nc-Si embedded in silicon nitride matrix was prepared by conventional plasma enhanced chemical vapor deposition system. We observed visible luminescence extended from red to blue region from nc-Si embedded in silicon nitride and the origin of the visible luminescence was attributed to the radiative recombination of electron-hole pairs formed in nc-Si. We demonstrated efficient LED based on nc-Si embedded in silicon nitride matrix by introducing the transparent doping layer of n-type SiC and ITO layer. We suggested that excitation occur by the tunneling of electrically inject carriers into nc-Si and the subsequent radiative recombination of electron-hole pairs in contrast to the case of SRSO. In addition, we demonstrated that the nc-Si LED with spacer layer of undoped SiC layer between active layer and n-type SiC layer shows enhanced carrier injection and increased output power above twofold compared to the device without undoped SiC layer.