Light emitting devices based on nanocrystalline-silicon multilayer structure

In this paper we report the visible–near-infrared light emission properties of nanocrystalline silicon (nc-Si) light emitting devices (LEDs) based on nc-Si/SiO2 multilayer structures. Multilayer structures of silicon-rich oxide (SRO) and SiO2 were grown by plasma enhanced chemical vapor deposition (PECVD) and studied by transmission electron microscopy (TEM) and ellipsometry. A higher nc-Si density in the multilayer samples than in the homogeneous sample was found by comparing photoluminescence (PL) intensities. The PL band located in the near-infrared region can be tuned by the size of nc-Si, which in the multilayer sample is controlled by the thickness of the SRO layer. The multilayer LED shows a much larger current density under low applied voltages than the LED based on a single thick layer. The significant lower driving voltage and enhanced light emission intensity suggest higher power efficiency in multilayer LED. It is believed that the improvement of the LED characteristics is due to the higher nc-Si density caused by the multilayer structure.