HfO₂ high- k solid-state incandescent devices: performance improvement using a Ti-embedded layer and observation of conductive paths as light-emitting sources

Solid-state incandescent light-emission devices (SSI-LEDs) with a metal-oxide-semiconductor structure are promising candidates for future broadband light-emission devices. In this work, the electrical and light-emission features of SSI-LEDs based on HfO₂ high- k thin films with or without the Ti-embedded layer on p-type silicon wafers have been studied. It turns out that the Ti-embedded layer can effectively reduce the turn-on voltage, thus improving the fluorescence efficiency of SSI-LEDs. The combination of scanning electron microscopy, atomic force microscope (AFM) and conductive AFM results unambiguously clarifies that conductive filaments, which are formed due to local thermal excitation during the forming process, are accompanied by the formation of pits on the HfO₂ surface and are responsible for the light emission. This work develops an effective approach to improving the luminescence performance of SSI-LEDs and experimentally explains the light-emitting mechanism of such devices, which is of great importance to eventually realizng broadband light-emitting devices with low power consumption. (paper)