Abstract: A radiation-emitting semiconductor diode in the InGaP/InAlGaP material system having a barrier for charge carriers situated between the active layer and one of the cladding layers. Such a diode has an emission wavelength between 0.6 and 0.7 .mu.m and is particularly suitable, when constructed as a diode laser, for serving as a radiation source in, for example, a system for reading and/or writing of optical discs, also because of an increased efficiency. The diode includes a barrier layer comprising only a single barrier layer of AlP, which can be manufactured with a good reproducibility and high yield. A thin AlP barrier layer, having a thickness less than 5 nm, for example 2.5 nm, still provides an excellent barrier.