Abstract The electroluminescent properties of Schottky diodes formed from single cyrstals of zinc selenide containing manganese, manganese and aluminium, aluminium or chlorine are discussed. All such diodes emitted a yellow band of variable width in reverse bias, the maximum of which lay between wavelengths of 5785 (2·14 eV) and 6050 A (2·05 eV). Optimum emission was obtained from ZnSe:Mn diodes where luminances of 500 ft L were achieved at a power efficiency of 1·9 × 10 −3%. Maximum efficiency of 3 × 10 −3% was obtained at a slightly lower luminance of 300 ft L. The ZnSe:Mn diodes exhibited the characteristic manganese emission in reverse bias in a narrow band centred at 5785 Å (2·14 eV). The presence of foreign donors such as aluminium reduced the luminance and the efficiency. This, coupled with a slight shift of the emission to longer wavelengths and a broadening of the emission band, is associated with the onset of the excitation of the self-activated emission which increased with increasing donor content. The self-activated emission in electroluminescence was found at 6300 A (1·97 eV) in ZnSe:Al and at 5900 A, (2·1 eV) in ZnSe:Cl. Forward bias electroluminescence was only observed in diodes which contained a relatively thick (∼200 A) insulating layer under the Schottky contact. Forward electroluminescence was at least an order of magnitude less bright than reverse EL.