A device may include a substrate and an active region. This active region may include a stack of semiconductor gain materials stacked along a stacking direction. The latter may extend substantially perpendicular to a plane of the substrate. The active region may be furthermore tapered so as to widen toward the substrate. In addition, the device may include a pair of doped layers semiconductor materials, the pair may include an n-doped layer and a p-doped layer arranged on the substrate and on opposite. The doped layers may be arranged on the substrate and on opposite, lateral sides of the tapered active region, respectively. The device may include an electron blocking layer, which may extend both at a first interface, between a p-doped layer and the substrate, and at a second interface, between the tapered active region and the p-doped layer, along a lateral side of the tapered active region.