Abstract: An epitaxial wafer for semiconductor light-emitting devices has an n-type substrate, on which are sequentially formed an n-type cladding layer, an active layer, a p-type cladding layer having Mg as a p-type dopant, and a p-type cap layer. The p-type cap layer has at least two Mg-doped and Zn-doped layers that are formed sequentially from the substrate side.

Abstract: An epitaxial wafer for semiconductor light-emitting devices has an n-type substrate, on which are sequentially formed an n-type cladding layer, an active layer, a p-type cladding layer having Mg as a p-type dopant, and a p-type cap layer. The p-type cap layer has at least two Mg-doped and Zn-doped layers that are formed sequentially from the substrate side.

Abstract: A method of fabricating diffraction gratings wherein a photomask is arranged on a substrate which is coated with a photoresist, light is to be incident thereupon at an acute angle relative to the normal direction of the photomask, and a bright/dark pattern is formed on said photoresist by the interference of the transmission light that has passed through the photomask and the diffraction light. The invention further deals with a photomask used for the above method.

Abstract: An optical information recording-reproducing system is provided using a laser diode with independent pulsating emission for recording and/or reproducing information, with the laser pulse period T (sec) and the distance L (m) between the semiconductor laser and information recording medium being set to meet the inequality:(n-1).times.0.8.times.c/2L<i/T<n.times.0.7.times.c/2Lwhere c is the velocity of light, and n is a natural number. By virtue of this arrangement, the relative noise intensity inherent to the optical feedback from the information recording medium is reduced below 10.sup.-3 Hz.sup.-1.

Abstract: A semiconductor device such as a semiconductor laser device or a transistor which is small in both threshold current and leakage current and exhibits no increase with time in the threshold current and leakage current can be obtained by incorporating pnp or npn junctions in a buried layer which coats an active region containing InGaAsP, forming the mid layer of the junctions with InGaAsP, adjusting the conductivity type of the mid layer with an implanted ion and specifying the energy band width of a semiconductor constituting the mid layer.

Abstract: A semiconductor laser having a double hetero structure comprises a cladding layer of In.sub.1-x-y Ga.sub.x Al.sub.y P.sub.1-z As.sub.z (0.ltoreq.x.ltoreq.1, 0.ltoreq.y.ltoreq.1, 0.ltoreq.z.ltoreq.0.5, 0.5.ltoreq.x+y.ltoreq.1) and an active layer of a strained-layer-superlattice of In.sub.1-x-y Ga.sub.x Al.sub.y P.sub.1-z As.sub.z (0.ltoreq.x.ltoreq.1, 0.ltoreq.y.ltoreq.1, 0.ltoreq.z.ltoreq.1, 0.ltoreq.x+y.ltoreq.1) system, thus enabling the lasing of wavelength ranges from infra-red to green.

Abstract: A novel method which enables a quaternary III-V group crystal to be readily formed on a III-V group crystal so that the former crystal lattice-matches with the latter crystal. More specifically, it is easy to produce a superlattice structure on a III-V group crystal substrate, the superlattice structure consisting of a first III-V group (hereinafter referred to as "III.sup.1 -V.sup.1 ") binary crystal layer which lattice-matches with the substrate, and a III-V group (III.sup.1 -III.sup.2 -V.sup.2) ternary crystal layer which similarly lattice-matches with the substrate. It is possible to obtain an even more stable superlattice layer by selecting the ratio between the film thickness of the (III.sup.1 -V.sup.1) crystal and the film thickness of the (III.sup.1 -III.sup.2 -V.sup.2) crystal so that, when the superlattice structure is mixed-crystallized spontaneously or by means of impurity doping, the mixed-crystallized composition lattice-matches with the previous crystal.