Si quantum dots and SiC quantum dots (SiC-QDs) co-doped Si-rich silicon carbide (Si C) based junction light-emitting diodes (LEDs) with blue light emission is demonstrated. By growing the SiC with plasma-enhanced chemical vapor deposition at relatively low temperature, the turn-on voltage of Si-rich Si C LEDs can be reduced to 6.1 V when thinning -SiC layer to 25 nm because of higher tunneling probability and lower series resistance. The electroluminescent (EL) power increases to 136 nW, however, which inversely attenuates due to the reduced SiC-QDs if the -Si C thickness further shrinks to 25 nm. The principle EL peak at 500 nm with narrower shape and blue-green emission pattern is attributed to the self-trapped excitons at surface states among SiC-QDs. The external quantum efficiency (EQE) of the Si-rich SiC LEDs with i-SiC thickness of 50 nm is up to 1.58 × 10% with enhanced carrier tunneling probability. The carrier injection efficiency is enhanced to 46% by increasing the doping concentration to 10 cm , leading to almost one order of magnitude improvement on the EQE of Si-rich Si C LEDs.