a q - switching injection laser is disclosed which includes integral emitter and saturable absorber sections of the semiconductive body . in one embodiment the emitter and absorber sections are separated by an interface region implanted with ions of a type and amount to significantly increase the resistivity at the interface . preferably , the implanted ions have energy levels spaced far enough from the conduction and valence bands of the semiconductive body such that charge carriers cannot be thermally excited between the conduction or valence bands and the energy level of the implanted ions . in another preferred embodiment , the saturable absorber section includes implanted ions of type and amount to increase the resistivity of the region , as compared to the emitter region , so as to give saturable absorber characteristic under available pumping conditions . likewise , preferably the implanted ion is selected such that its energy levels are sufficiently separated from the valence and conduction bands so as to prevent thermal excitation from transferring charge carriers between valance and conduction bands and the energy levels of the implanted ion . in a specific embodiment , in a gaas injection laser doped with ge or si , the implanted ion may be selected from the group including o , cr and fe .