Enhanced room-temperature electroluminescence from a germanium waveguide on a silicon-on-insulator diode with a silicon nitride stressor.

Germanium (Ge) is an attractive material for monolithic light sources on a silicon chip. Introduction of tensile strain using a silicon nitride (SiN) stressor is a promising means for Ge-based light sources due to the enhancement of direct band gap recombination. We propose a device structure that enables current injection from a silicon-on-insulator (SOI) diode to a Ge waveguide with a SiN stressor formed by a simple fabrication process. Direct-band-gap electroluminescence and direct-band-gap shrinkage due to the applied SiN stressor was confirmed. Intensity of electroluminescence from the Ge waveguide with the SiN stressor was about three times higher than that corresponding to the device without the SiN stressor.