The invention relates to an optoelectronic device, having at least one microwire or nanowire extending along a longitudinal axis substantially orthogonal to a plane of a substrate, and including: a first doped portion produced from a first semiconductor compound; an active zone extending from the first doped portion; a second doped portion, at least partially covering the active zone; characterised in that the active zone comprises a wider single-crystal portion: formed of a single crystal of a second semiconductor compound and at least one additional element; extending from an upper face of one end of the first doped portion, and having a mean diameter greater than that of the first doped portion.