Abstract: At a gate electrode formed on a compound semiconductor layer with a Schottky junction, a diffusion preventing layer made of TixW1-xN (0<x<1) for suppressing the metal of a low-resistance metal layer from diffusing to the compound semiconductor layer is provided between a Ni layer forming a Schottky barrier with the compound semiconductor layer and the low-resistance metal layer, and thus an increase in the leak current at the gate electrode is suppressed.

Abstract: A tunable laser module includes a tunable laser section including a gain medium and a wavelength filter having a periodic characteristic which brings about a discontinuous variation of an oscillation wavelength, and a monitoring section adapted to output a monitoring signal which periodically varies in response to the oscillation wavelength of the tunable laser section. The monitoring section includes a monitoring wavelength filter having a periodic characteristic which defines the monitoring signal. The relationship between the period of the wavelength filter and the period of the monitoring wavelength filter is set such that the monitoring signal varies when the oscillation wavelength varies discontinuously.

Abstract: An optical semiconductor device includes a waveguide having one or more first segments having a region that includes a diffractive grating and another region combined to the region, one or more second segments having a region that includes a diffractive grating and another region combined to the region and a plurality of third segments having a region the includes a diffractive grating and another region combined to the region, a length of the second segment being different from that of the first segment, a length of the third segment being shown as L3=L1+(L2?L1)×K1 in which 0.3?K1?0.7, L1 is a length of the first segment, L2 is a length of the second segment and L3 is a length of the third segment; and a refractive index control portion controlling refractive index of the first segment through the third segments.

Abstract: A testing method of a wavelength-tunable laser having a resonator including wavelength selection portions having wavelength property different from each other includes a first step of controlling the wavelength-tunable laser so as to oscillate at a given wavelength according to an initial setting value, a second step of tuning the wavelength property of the wavelength selection portions and detecting discontinuity point of gain-condition-changing of the wavelength-tunable laser, and a third step of obtaining a stable operating point of the wavelength selection portion according to a limiting point of an oscillation condition at the given wavelength, the limiting point being a point when the discontinuity point is detected.

Abstract: A testing system including a plurality of test applying portions that operate a test device for outputting an output signal; a plurality of testing portions that test the output signal of the test device; and a switch portion that switches the output signal between the test applying portions and the testing portions. The testing portions each have a test information portion that outputs test item information which includes a test capability of the testing portion, and have a test performing portion which is selected under the test item information that receives the output signal from the test applying portion through the switch portion, and performs a test under a designated test item.

Abstract: A laser module includes a semiconductor laser, an output optical system provided on an optical output side of the semiconductor laser, a temperature detecting element that detects a temperature of the output optical system; and an output controller that calculates a drive current to set an optical output intensity of the laser module at a desired value on the basis of temperature information obtained by the temperature detecting element, and outputs the drive current to the semiconductor laser.

Abstract: An optical semiconductor device includes a waveguide having one or more first segments having a region that includes a diffractive grating and another region combined to the region, one or more second segments having a region that includes a diffractive grating and another region combined to the region and a plurality of third segments having a region the includes a diffractive grating and another region combined to the region, a length of the second segment being different from that of the first segment, a length of the third segment being shown as L3=L1+(L2?L1)×K1 in which 0.3?K1?0.7, L1 is a length of the first segment, L2 is a length of the second segment and L3 is a length of the third segment; and a refractive index control portion controlling refractive index of the first segment through the third segments.

Abstract: In order to improve reliability by preventing edge breakdown in a semiconductor photodetector having a mesa structure such as a mesa APD, the semiconductor photodetector includes a mesa structure formed on a first semiconductor layer of the first conduction type formed on a semiconductor substrate, the mesa structure including a light absorbing layer for absorbing light, an electric field buffer layer for dropping an electric field intensity, an avalanche multiplication layer for causing avalanche multiplication to occur, and a second semiconductor layer of the second conduction type, wherein the thickness of the avalanche multiplication layer at the portion in the vicinity of the side face of the mesa structure is made thinner than the thickness at the central portion of the mesa structure.

Abstract: A semiconductor device includes: a nitride semiconductor layer including a channel layer, a Schottky electrode that contacts the nitride semiconductor layer and contains indium, and an ohmic electrode that contacts the channel layer. The nitride semiconductor layer includes a layer that contacts the Schottky electrode and contains AlGaN, InAlGaN or GaN. The Schottky electrode that contains indium includes one of an indium oxide layer and an indium tin oxide layer.

Abstract: Fluoroalcohol compounds of formula (4) are prepared by reacting a fluorine compound of formula (1) with reducing agents or organometallic reagents of formulas (2) and (3) wherein R1 is H or a monovalent C1-C20 hydrocarbon group in which any —CH2— moiety may be replaced by —O— or —C(?O)—, R2 is H or a monovalent C1-C6 hydrocarbon group, R3 and R4 are H or a monovalent C1-C8 hydrocarbon group, and M1 is Li, Na, K, Mg, Zn, Al, B, or Si. From the fluoroalcohol compounds, fluorinated monomers can be produced in a simple and economic way, which are useful in producing polymers for the formulation of radiation-sensitive resist compositions.

Abstract: In a circuit module for a high frequency, a resistance film is formed on a side of a semiconductor circuit chip, mounted above a dielectric substrate through ground metal layers, opposite to the dielectric substrate. A distance from the ground metal layer to the resistance film is a ¼ wavelength at a predetermined frequency, and the resistance film has a sheet resistance equal to a characteristic impedance of air. A second dielectric substrate with the metal layer formed on a side opposite to the resistance film can be mounted. When being adhered to the second dielectric substrate, the resistance film has a characteristic impedance determined by a permittivity of a material of the semiconductor circuit chip. When being formed in space from the semiconductor circuit chip, the resistance film has a sheet resistance equal to a characteristic impedance of air. The thickness of the second dielectric substrate is a ¼ wavelength in a desired frequency.

Abstract: A fabrication method of a semiconductor device includes forming a silicon nitride layer on a compound semiconductor layer with a plasma CVD method and selectively treating the compound semiconductor layer with use of the silicon nitride layer for a mask. The silicon nitride layer has a refraction index of less than 1.85. The compound semiconductor layer includes Ga.

Abstract: A semiconductor device includes a lower pad layer, an insulating layer and an upper pad layer. The lower pad layer is provided on a semiconductor substrate. The insulating layer is away from a surrounding of the lower pad layer so that a space having a recess on a surface between the lower pad layer and the insulating layer is formed. The upper pad layer covers over the lower pad layer and the space, extends to an upper face of the insulating layer, and has an area larger than that of the lower pad layer.

Abstract: A switch circuit includes: a first FET that is connected to one of an input terminal and an output terminal, and performs ON/OFF operation under the control of a gate electrode connected to a control terminal; and a second FET that is connected between the first FET and the other one of the input terminal and the output terminal, and performs ON/OFF operation under the control of a gate electrode connected to the control terminal. The first FET has a higher gate backward breakdown voltage than that of the second FET. Alternatively, the first FET has lower OFF capacitance than that of the second FET.

Abstract: A method of controlling a semiconductor laser that has a plurality of wavelength selection portions having a different wavelength property from each other and is mounted on a temperature control device, including: a first step of correcting a temperature of the temperature control device according to a detected output wavelength of the semiconductor laser; and a second step of controlling at least one of the wavelength selection portions so that changing amount differentials between each wavelength property of the plurality of the wavelength selection portions is reduced, the changing amount differential being caused by correcting the temperature of the temperature control device.

Abstract: An optical device includes an optical element, a detector and a controller. The optical element has an optical waveguide. Refractive index of the optical waveguide is controlled by a heater. A temperature of the optical element is controlled by a temperature control device. The detector detects a current flowing in the heater and/or a voltage applied to the heater. The controller controls an electrical power provided to the heater so as to be kept constant according to the detection result of the detector.

Abstract: An optical semiconductor module with a light receiving element with an upper and side light receiving face and a light emitting element mounted on the same mounting carrier. The light receiving element has a light receiving face on an upper face and a side face covered with an antireflection film. The mounting unit has the light emitting element and the light receiving element mounted so that they encompass a positional relationship that the light emitted from the light emitting element is optically connected at least on the light receiving face of the side face of the light receiving element.

Abstract: A method of manufacturing a semiconductor device includes: forming a mask layer on a layer that is to be subjected to etching and contains at least one of silicon carbonate, silicon oxide, sapphire, gallium nitride, aluminum gallium nitride, indium gallium nitride, and aluminum nitride, the mask layer having an opening and including a nickel chrome film, a gold film, and a nickel film in this order when seen from the layer to be subjected to etching; and performing etching on the layer to be subjected to etching, with the mask layer serving as a mask.

Abstract: A testing system includes a plurality of test applying portions and a plurality of testing portions, each test applying portion having a test device that generates an output signal and each testing portion tests the output signal of the test device, in response to the test applying portion. The testing system further includes a switch portion that switches the output signal of the test device between the test applying portions and the testing portions. The test applying portion has a selecting portion that selects the testing portion through the switch portion for testing the output signal according to test item information, the test item information including information about a test capability of the testing portion.

Abstract: An electronic circuit includes a differential amplifier circuit, a first smoothing circuit, a second smoothing circuit and a first switch. The differential amplifier circuit receives a digital input signal and a reference signal. The first smoothing circuit smoothes the digital input signal with a first capacitance value. The second smoothing circuit smoothes the digital input signal with a second capacitance value larger than the first capacitance value. The first switch selects one of output signals from the first smoothing circuit and the second smoothing circuit as the reference signal.