The field control of the luminescent characteristics is investigated with three‐terminal field‐effect light‐emitting devices with superlattice buffer layers, showing a high‐speed switching (∼0.8 ns) of emission intensity, free from lifetime limitation at room temperature and a high quantum yield of the emission intensity, i.e., an external efficiency &eegr;ex≥1%. It is demonstrated that a combination of the field control of radiative lifetime with carrier leakage results in a high‐speed modulation of luminescence intensity under a fixed carrier population in the active layer, unchanged with and without electric fields.