We observed current-injected spectrally narrowed emissions (SNEs) from a light-emitting field-effect transistor (LEFET) characterized by both layered organic semiconductor crystals and a two-dimensional (2D) diffraction grating. The grating fabricated using nanoimprint lithography had circular air holes forming a triangular lattice. We laminated the p- and n-type crystals in this order on the grating and deposited heterogeneous metal drain and source electrodes. The several SNE peaks were definitively observed when we applied square-wave alternating-current voltages to the gate contact.