Si-Based GaN Light-Emitting Diodes with MoS2 Nanosheet-Decorated Fabry–Perot Waveguide Structure

III–V semiconductor light-emitting diodes (LEDs) on Si substrates, suitable for large-scale and large-wafer-size manufacturing, are a convenient option for on-chip light sources. Here, we present the design and fabrication of a MoS2 nanosheet-decorated InGaN/AlGaN/GaN LED on a Si substrate with a Fabry–Perot waveguide, utilizing standard microfabrication processes. We assess the voltage–current characteristics, electroluminescence (EL) properties, polarization properties, chrominance, and surface temperature of the device. The MoS2 layer's spectrum filtering effect and the waveguide's interference effect influence the EL properties of GaN LED. The MoS2-decorated LED device presented different properties than the bare LED in terms of a higher turn-on voltage, uniform emission pattern, lower surface temperature, and higher polarizability. Besides, the underlying mechanism for spectral modulation is studied. The MoS2-decorated device demonstrates an EL peak near 417 nm, with a high side mode suppression ratio and full width at half-maximum (FWHM) < 1 nm. Our study offers insights into the potential realization of light sources with narrowed spectra using GaN LEDs based on Si materials.