Voltage-controlled electroluminescence from SiO2 films containing Ge nanocrystals and its mechanism

Luminescent SiO2 films containing Ge nanocrystals are fabricated by using G e ion implantation, and metaloxide-semiconductor structures employing these films as the active layers show yellow electroluminescence (EL) under both forward and reverse biases. The EL spectra are strongly dependent on the a pplied voltage, but slightly on the mean size of Ge nanocrystals. When the forward bias increases towards 30 V, the EL spectral peak shifts from 590 n m to 485 nm. It is assumed that the EL originates from the recombination of injected electrons and holes in Ge nanocrystals near the Si/SiO2 interface , or through luminescent centers in the SiO2 matrix near the SiO2/metal int erface. The mismatch of the injection amounts between holes and electrons r esults in the low EL efficiency.