Abstract: A bipolar transistor circuit element includes a semiconductor substrate; successively disposed on the substrate, a base layer, an emitter layer, and a collector layer; a bipolar transistor formed from parts of the collector, base, and emitter layers and including a base electrode electrically connected to the base layer and a base electrode pad for making an external connection to the base layer; a base ballasting resistor formed from a part of the base layer isolated from the bipolar transistor and electrically connecting the base electrode to the base electrode pad; and a base parallel capacitor connected in parallel with the base ballasting resistor wherein the base parallel capacitor includes part of the base input pad, a dielectric film disposed on part of the base electrode pad, and a second electrode disposed on the dielectric layer opposite the base electrode pad and electrically connected to the emitter electrode of the bipolar transistor.

Abstract: A laser diode in accordance with the present invention comprises: a substrate (11) of p-GaAs; a current constricting layer (12) of n-GaAs formed with a slit (13) over the substrate, wherein the slit is opened through the constricting layer and separates the constricting layer into two areas; a liner(s) (21) of p-GaAs formed on at least both the inner side walls of the slit; a lower clad layer (14) of p-Ga.sub.0.6 Al.sub.0.4 As formed over the constricting layer, burying the slit; an active layer (15) of p-Ga.sub.0.9 Al.sub.0.1 As which is formed over the lower clad layer and has a refractive index higher than that of the lower clad layer; and an upper clad layer of n-Ga.sub.0.6 Al.sub.0.4 As which is formed over the active layer and has a refractive index lower than that of the active layer.

Abstract: A surface emitting semiconductor laser comprising an active layer having a convex portion is disclosed in this specification. This surface emitting semiconductor laser has a structure in which an n-type first semiconductor layer, a p-type active layer and a p-type second semiconductor layer are formed one upon another on one surface of an n-type semiconductor substrate having a concave portion. The active layer has a convex portion corresponding to the concave portion of the semiconductor substrate. On the other surface of the semiconductor substrate, there is provided a negative electrode in the form of a ring surrounding the above stated concave portion. A positive electrode is electrically connected to the above stated second semiconductor layer through an insulating layer having a contact hole. A forbidden band width of the material forming the active layer is smaller than the respective forbidden band widths of the materials forming the other semiconductor layers.

Abstract: A semiconductor laser is provided with an active layer which is bent at an angle at both ends of the resonator so that both ends of the waveguide path are formed by semiconductor cladding layers. The structure is effective in increasing the obtainable optical density while decreasing absorption at the waveguide ends.

Abstract: A surface-emitting injection type laser device has a semiconductor wafer including a first and a second main face opposite to each other and an active layer located on the side of the first main face. A single mode optical fiber chip has a first and second end surface perpendicular to its optical axis and is disposed on the semiconductor wafer with the first end surface contacting the second main face through a reflection preventing film. A dielectric film is disposed on the second end surface of the optical fiber chip to increase the reflection power at the second end surface and forming a resonator with the first main face of the semiconductor wafer.

Abstract: A first N-AlGaAs and a second N-GaAs layer are successively grown on an I-GaAs substrate. A third N-AlGaAs, a fourth P-AlGaAs and a fifth N-GaAs layer superpose one another on the second layer except for one lateral portion. Those portions of the five layers remote from the exposed second layer portion are changed into a P.sup.+ type and surrounded by a P zone. A positive and a negative electrode are located on the fifth layer and the exposed second layer portion respectively. The negative electrode is nearest to a laser region located in the second layer and can be secured to a heat sink.

Abstract: A P type semiconductor layer is epitaxially grown on an N.sup.+ type semiconductor substrate to form a PN junction between them so as to expose its circumference to the peripheral surface of the substrate. The P type layer is formed into a mesa having a tilted surface to which the circumference of the PN junction is exposed. Then an N.sup.+ type diffusion layer is disposed on the tilted mesa surface to protect the PN junction.

Abstract: An avalanche photodiode comprises a photo-electric conversion region made of a semiconductor having an energy band gap smaller than the photon energy and a carrier multiplying region made of a semiconductor that differs from the semiconductor of the photo-electric conversion region. The different semiconductors for imparting superior functions to the regions are used to improve the quantum efficiency in the photo-electric conversion region and to decrease noise in the carrier multiplying region.

Abstract: An SiO.sub.2 film doped with an impurity is formed on at least one portion of a surface of a semiconductor wafer. The wafer is selectively etched after a protective film for selective etching is disposed into a predetermined pattern on the SiO.sub.2 film. The impurity included in the SiO.sub.2 film can be diffused into the wafer to form a PN junction in the latter. Then the wafer is selectively etched until that surface of the wafer to which the PN junction is exposed is bevelled.