Visible electroluminescence from silicon nanocrystals embedded in amorphous silicon nitride matrix

Visible electroluminescence from silicon nanocrystals (Si-NCs) embedded in amorphous silicon nitride (a-SiNx) films has been observed. The Si-NC∕a-SiNx films were deposited by evaporating silicon from electron gun into the inductively coupled plasma of nitrogen. The density of Si-NCs in the a-SiNx matrix was around 1012cm−2. Strong room temperature photoluminescence was observed in 2.8 and 3.0eV, different from literature values. The electroluminescence (EL) devices were fabricated with Si-NCs∕a-SiNx film as the active layer using the Al or Ca∕Ag 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-SiNx matrix. For the device with Ca∕Ag cathode, the turn-on voltage was as low as 10V and the EL efficiency was about 1.6×10−1 Cd∕A. The EL spectra consisted of two broad peaks centered around 2.5 and 2.8eV. Our results demonstrate that Si-NCs∕a-SiNx nanocomposite films have potentials to be fabricated into electroluminescence devices using the low work function cathode.