A semiconductor light-emitting device fabricated in the (Al,Ga,In)N materials system has an active region for light emission (3) comprising InGaN quantum dots or InGaN quantum wires. An AlGaN layer (6) is provided on a substrate side of the active region. This increases the optical output of the light-emitting device. This increased optical output is believed to result from the AlxGa1-xN layer serving, in use, to promote the injection of carriers into the active region.