In this paper, we present a room-temperature electroluminescence (EL) study of amorphous nonstoichiometric silicon nitride ( SiN _X) films. The light-emitting device is formed by an ITO / SiN _X/p -type silicon structure. EL shows a yellowish broad emission spectrum with a power efficiency of 10^-6 . The EL peak energy depends on the bias voltage rather than on the silicon content in SiN _X . By fitting the current-voltage characteristic with existing models, we found that under high voltages the Poole–Frenkel hole conduction is the main carrier transport mechanism in these devices. Injected electrons are captured by silicon dangling bonds ( K center) and recombine with holes, which are localized in valence band tail states. Unbalanced hole and electron injection and nonradiative recombination are the main constraints on the EL efficiency of SiN _X .