A light-emitting-diode array includes a non-doped compound semiconductor layer between a substrate and a first compound semiconductor layer. A plurality of isolation regions extend from the first compound semiconductor layer to the surface of the non-doped compound semiconductor layer, and provide separation into isolated block regions each containing an equal number of diffusion regions. A plurality of shared electrode lines are connected to the diffusion regions in a plurality of the block regions, in such a relationship that diffusion regions selected from each of the block regions are connected to a common shared electrode. At least a surface portion of the substrate is formed of silicon. The density of the diffusion regions can be increased without increasing the number of the electrode pads. Moreover, the substrate is free from breakage or cracks.