Long-wavelength semiconductor lasers

A semiconductor laser wherein a wide range of laser emission wavelengths can be obtained by varying the composition of monocrystalline alloys employed as semiconductor material. The semiconductor structure comprises on a monocrystalline indium phosphide substrate of a predetermined conductivity type successive epitaxial layers consisting of a first confinement layer of the same conductivity type, an active layer having the formula (Gax Al1-x)0.47 In0.53 As where x is within the range of 0 to 0.27, and a second confinement layer of opposite conductivity type. The confinement layers are composed of either InP or a ternary alloy Al0.47 In0.53 As or a quaternary alloy Gax' Al1-x' Asy' Sb1-y' where x' and y' are chosen so that the material should have a predetermined crystal lattice and an energy gap of greater width than the substrate material.