Light-emitting diode (LED) comprising a translucent substrate of α-Al2O3 or SiC and a first layer of a light-emitting semiconductor material grown on a first side of said substrate, a first electrode and a second electrode, wherein said substrate is polycrystalline. The average grain size of the polycrystalline substrate is preferably of the same order as the wavelength of the light emitted by the semiconductor material during use of the LED.