a tensile stress which is effectively greater than the compression stress so that the resultant net stress in the active layer 2 is a tensile stress the stress situation in the active layer 2 necessary for the invention is achieved in this example as listed in the table below u03b4a a therein is the relative difference in lattice constant compared with the substrate 11 and d is the thickness of the layer in question the resultant tensile stress in the active layer 2 is 2 16 0 5 1 8 1 8 nm the absolute value of which is smaller in this case much smaller than 30 nm this means that there is practically no risk of stress induced defects occurring in the active layer 2 the stress relaxation in quantum well layer 2a and barrier layers 2b which occurs in the laser near the end faces 3 and the overcompensation of the compression stress cause a greater bandgap e g near the end faces 30 in the active layer so that the absorption of radiation generated in the active region decreases strongly near the end face 30 end face or mirror degradation in the laser according to the invention is substantially lower as a result of this than in the known laser and the former has a considerably.