Abstract: A semiconductor light emitting diode includes a first conductivity type compound semiconductor substrate, a first conductivity type lower cladding layer, an active layer of undoped AlGaInP or multiple quantum well structure, and a second conductivity type upper cladding structure. The upper cladding structure comprises an (Al.sub.x Ga.sub.1-x).sub.y In.sub.1-y P four element compound semiconductor material. The improvement is that the upper cladding structure has a thin and very high resistivity layer inside.

Abstract: An improved structure of a laser indicator includes an outer tube, a cover cap, a focus adjusting device, an optical lens, and a circuit board having a laser diode disposed thereon. The outer tube and the cover cap are joined to form a rod-shaped indicator housing. The optical lens and the laser diode are provided inside the focus adjusting device, which is comprised of an inner cover and an outer cover working in conjunction with a metallic spring. The laser diode is fittingly disposed inside the inner cover, while the outer cover is screwably connected to the outer cover. The spring is disposed between the inner cover and the optical lens. One end of the outer cover is screwably coupled to the cover cap, while the other end thereof forms a smooth holding surface to facilitate turning of the outer cover in focus adjustment.

Abstract: A light emitting diode comprises a multiple quantum well structure. The light emitting diode has a first conductivity type GaAs substrate, an AlGaInP lower cladding layer of the first conductivity type, a multiple quantum well structure, an AlGaInP upper cladding layer of a second conductivity type, and a window structure of the second conductivity type. The multiple quantum well structure comprises a plurality of AlGaInP quantum well layers and barrier layers being stacked alternatively on each other. The window structure including a thin layer having low energy band gap and high conductivity GaAs or GaInP, and a thicker layer having high energy band gap and transparent GaP containing a small amount of In. The use of multiple quantum well structure improves the light intensity and the Iv-I curve linearity of the light emitting diode.

Abstract: A light emitting diode includes a first conductivity type GaAs substrate having a second conductivity type region as a current blocking layer. A first conductivity type distributed Bragg reflector layer is formed on the GaAs substrate. An AlGaInP double heterostructure including a lower cladding AlGaInP layer of the first conductivity type, an undoped active AlGaInP layer, and an upper cladding AlGaInP layer of the second conductivity type is grown on top of the distributed Bragg reflector layer. The undoped active AlGaInP layer can also be replaced by a multi-layer quantum well structure of AlGaInP or a strained multi-layer quantum well structure of AlGaInP. A second conductivity type layer of low energy band gap and high conductivity material is formed on the AlGaInP double heterostructure. A GaP window layer of the second conductivity type is then formed on top of the low energy band gap layer.

Abstract: A light emitting diode is provided with a window layer of ZnSSe semiconductor material having a second conductivity type. The second conductivity type ZnSSe window layer has a low electrical resistivity so that it can be used as a current spreading layer, and a bandgap higher than that of the active layer so that it is transparent to light emitted from the active layers. The second conductivity type ZnSSe window layer can be doped with a donor concentration of more than 10.sup.18 cm.sup.-3. Furthermore, its lattice constant is close to that of the active layers and confining layers so that deterioration in optical characteristic due to lattice mismatch is minimized.

Abstract: A process for growing a gallium arsenide single crystal from a polycrystalline gallium arsenide by the horizontal Bridgman technique includes (a) melting the polycrystalline gallium arsenide in a quartz boat which is placed in a quartz tube, at a temperature greater than 1238 deg C. but lower than the melting point of quartz, (b) decreasing the temperature of the melt of gallium arsenide from the seed/melt interface by moving a furnace to crystallize the melt, and (c) annealing the crystallized gallium arsenide during the crystal growth process at a temperature of 1100-1220 deg C.; wherein the above steps are carried out in the absence of an As vapor pressure controlling zone which is kept at a temperature of about 617 deg C. Due to the anealing step, the thermal stress is small and the dislocation hardly occurs. A short quartz tube can be employed due to the absence of the As zone.