Silicon-rich silicon nitride (SRSN) films were prepared on p-type silicon substrates using plasmaenhanced chemical vapor deposition (PECVD). Small size (similar to 3 nm) amorphous silicon quantum dots (a-Si QDs) were obtained after 1100 degrees C annealing. Two different excitation sources, namely 325 nm and 532 nm lasers, were introduced to investigate the photoluminescence (PL) properties. The PL bands pumped by 325 nm laser at similar to 2.90 eV and similar to 1.80 eV were contributed to the radiative centers from N dangling bonds (DBs), while the dominant PL bands at 2.10 eV were ascribed to the instinct PL centers in the nitride matrix. However, PL emissions from band tail luminescence and quantum confined effect (QCE) in a-Si QDs were found under the excitation of 532 nm laser. Light emitting diode (LED) with ITO/SiNx/p-Si/A1 structure was fabricated. Intensely red light emission was observed by naked eyes at room temperature under forward 20 V. Three different carrier transport mechanisms, namely Poole-Frenkel (P-F) tunneling, Fowler-Nordheim (F-N) tunneling and space charge limited current (SCLC), were found to fit different electric field regions. These results help to understand the PL mechanisms and to optimize the fabrication of a-Si QD LED. (C) 2015 Elsevier B.V. All rights reserved.