Patent US 3,986,194

An injection-type laser light emitting semiconductor device comprising a main unit in the shape of a generally rectangular parallelepiped comprising a layer of a magnetic semiconductor for emitting laser light and at least one layer of semiconductor having the same crystal structure and substantially the same lattice constant as those of the magnetic semiconductor and also having a greater optical energy gap than that of the magnetic semiconductor, both end surface of the main unit perpendicular to the coalescing surface of the two layers serving as reflecting plates for the emission of laser light, and a pair of electrodes fixed ohmically to the under surface and top surface of the main unit. This device affords laser light whose wavelength varies over a relatively wide range according to changes in the oprical energy gap of the magnetic semiconductor as a result of changing the temperature and/or applied magnetic field.