Visible electroluminescence from silicon nanocrystals embedded in amorphous silicon nitride matrix

Visible electroluminescence from silicon nanocrystals (Si-NCs) embedded in amorphous silicon nitride (a-Si Nx) films has been observed. The Si-NCa-Si Nx films were deposited by evaporating silicon from electron gun into the inductively coupled plasma of nitrogen. The density of Si-NCs in the a-Si Nx matrix was around 1012 cm-2. Strong room temperature photoluminescence was observed in 2.8 and 3.0 eV, different from literature values. The electroluminescence (EL) devices were fabricated with Si-NCsa-Si Nx film as the active layer using the Al or CaAg cathode and the indium tin oxide anode. Through tunneling, the electrons and holes were respectively injected from the cathode and anode into Si-NCs and confined within Si-NCs for light emission by the high band gap a-Si Nx matrix. For the device with CaAg cathode, the turn-on voltage was as low as 10 V and the EL efficiency was about 1.6× 10-1 CdA. The EL spectra consisted of two broad peaks centered around 2.5 and 2.8 eV. Our results demonstrate that Si-NCsa-Si Nx nanocomposite films have potentials to be fabricated into electroluminescence devices using the low work function cathode.