A semiconductor quantized layered structure comprising first and second different semiconductor materials comprising compound semiconductors from both the Group III and Group V elements and forming a plurality of alternate layers, each interfaced to its adjacent layer in a semiconductor homojunction or heterojunction. The bottom of the conduction bands of the first and second materials are at different energy levels and the tops of the valence bands of the first and second materials are at different energy levels. The bottoms of the conduction bands of the first and second materials form a plurality of serially arranged potential wells and barriers due to differences in the band structures of the different materials forming alternate layers and the interfacing of the layers forming heterojunctions so that the thinness of the layers will spatially localize electrons to obtain quantized electron states in one dimension transverse to the longitudinal extent of said layers. The invention is characterized in that the first material is an indirect bandgap material and optimized luminescence efficiency of the first material is achieved by adjusting the thickness of the layers comprising the first material to be less than the mean free path of an electron in the first material in the absence of the second material. Three dimensional quantized electron states may be provided in certain layers of the quantized layered structure with the incorporation of an impurity, such as, a donor or acceptor impurity or an isoelectronic impurity forming isoelectronic centers (IEC) in the indirect bandgap semiconductor material. Such an incorporation may be in each layer of the first and second materials or only in the alternate layers of the lower indirect bandgap material. Alternatively, the impurity may be in a predetermined periodic alternate of layers of the same indirect bandgap material, e.g., in one layer out of three, in alternate layers of a plurality of layers or in every n.sup.th layer or every n.sup.th group of layers where n may be any integer.