Influence of surface electrode on luminescent properties of nanocrystalline silicon electroluminescent device

We describe the electrical and luminescence properties of nanocrystalline silicon (nc-Si) based red electroluminescent (EL) devices using an indium tin oxide (ITO) and/or gold (Au) films as a surface electrode, and the variation in the transmittance and resistivity of two electrodes with various film thicknesses. The increase in the film thickness from 50 to 200 nm of the ITO electrode led to the lowering of resistivity from 2.0 x 10(-3) to 9.1 x 10(-4) omega cm and almost the same value (83-92%) of transmittance in the red region. On the other hand, the Au electrode was lowered the resistivity from 1.8 x 10(-4) to 1.6 x 10(-5) omega cm and the transmittance in the red region from 42 to 1.8% with increasing the film thickness from 10 to 80 nm. Moreover, the red luminescence from the EL devices using the ITO and/or Au electrodes having thickness of 200 and 10 nm, respectively, obtained by applying the direct current forward voltage above 4.5 and 2.5 V and/or by flowing the forward current density above 53 and 38 mA/cm2, respectively. However, the luminescence intensity of EL device with the ITO electrode strengthened more than about one order of magnitude in comparison to that of the EL device with the Au electrode. This was due to the high value of transmittance in the red region of the ITO electrode. We suggest that the ITO electrode is an optimum surface electrode for the realization of nc-Si based EL device with the high brightness.