Abstract: A semiconductor laser device in which semiconductor layers of an n-type cladding layer, a quantum well active layer 106, a p-type cladding layer, and an intermediate layer are formed on an n-type GaAs substrate in successive order, and a mixed-crystal is formed in a region except the semiconductor layers of the contact layer and the lower part of the contact layer by diffusing Si into the structure from above the intermediate layer, characterized in that the contact layer and the intermediate layer are made of n-type or nonconductive semiconductor material, and a p-type low-resistance region, formed by diffusing Zn into the structure from above the contact layer, is profiled so as not to overlap with the mixed-crystal region formed by Si diffusion.

Abstract: A semiconductor laser device in which semiconductor layers of an n-type cladding layer, a quantum well active layer 106, a p-type cladding layer, and an intermediate layer are formed on an n-type GaAs substrate in successive order, and a mixed-crystal is formed in a region except the semiconductor layers of the contact layer and the lower part of the contact layer by diffusing Si into the structure from above the intermediate layer, characterized in that the contact layer and the intermediate layer are made of n-type or nonconductive semiconductor material, and a p-type low-resistance region, formed by diffusing Zn into the structure from above the contact layer, is profiled so as not to overlap with the mixed-crystal region formed by Si diffusion.

Abstract: In a semiconductor laser device according to the invention, a clad layer includes first clad layers, each of which has a greater band gap than an active layer and has a thickness of 0.003 to 0.3 .mu.m, and second clad layers each of which has a lower refractive index than the active layer, and the first clad layers are disposed nearer to the active layer than the second clad layers, respectively. In this structure, the first clad layers confine carriers in the active layer while the second clad layers confine the light in the active layer. Since each of the first clad layers is formed of a thin film, the carriers are hard to move outwardly from the active layer due to the tunnel phenomenon thereof and, even if the lattice constant thereof is slightly different, the first clad layer can be lattice matched to a substrate. For this reason, the materials of the second clad layers can be selected without taking into consideration the size of the band gap thereof.

Abstract: It is an object of the present invention to provide a highly efficient semiconductor laser unit having excellent temperature characteristics, in which electrons or holes are suppressed from overflowing from the active layer to the cladding layers while the threshold of current density is maintained low. The present invention is to provide a semiconductor laser unit fundamentally composed of an active layer and cladding layers in which the active layer is interposed between the cladding layers the semiconductor laser unit comprising: a multiquantum barrier layer including well layers and barrier layers disposed between the active layer and the cladding layers or disposed in the cladding layers close to the active layer, wherein the well and barrier layers have a high reflectivity with respect to the electrons and holes at a position close to .GAMMA.

Abstract: A semiconductor laser device having an active layer which is comprised of a quantum well layer formed of a mixed crystal material, and barrier layers provided on both sides of the quantum well layer in such a manner as to sandwich the same, is characterized in that Ge is thermally diffused in a portion of the active layer to disorder the quantum well layer and the barrier layers at that portion so as to form a non-light-emitting area with a low refractive index, while the quantum well layer and the barrier layers at a portion where Ge is not diffused is formed as a refractive index waveguide which is a light-emitting area.