An all-silicon in-plane micron-size electrically driven resonant cavity light emitting device (RCLED) based on slotted waveguide is proposed and modeled. The device consists of a microring resonator formed by Si/SiO2 slot-waveguide with a low-index electroluminescent material (erbium-doped SiO2) in the slot region. The geometry of the slot-waveguide permits the definition of a metal-oxide-semiconductor (MOS) configuration for the electrical excitation of the active material. Simulations predict a quality factor Q of 6,700 for a 20-μm-radius electrically driven microring RCLED capable to operate at a very low bias current of 0.75 nA. Lasing conditions are also discussed.