Sharp Kabushiki Kaisha Corporation

Eiji Yamada

Tetsuo Iwaki

Takeshi Kamikawa

Masahiro Araki

Toshiaki Harada

Ikuo Nakano

Tohru Okuda

Mayuko Fudeta

Hitoshi Takeuchi

Yoshika Kaneko

Chiaki Yamawaki

Toshihisa Tanaka

Disclosed is a nitride semiconductor light-emitting element comprising a p-type nitride semiconductor layer 1, a p-type nitride semiconductor layer 2, and a p-type nitride semiconductor layer 3 placed in order above a nitride semiconductor active layer, wherein the p-type nitride semiconductor layer 1 and p-type nitride semiconductor layer 2 each contain A1, the average A1 composition of the p-type nitride semiconductor layer 1 is equivalent to the average A1 composition of the p-type nitride semiconductor layer 2, the p-type nitride semiconductor layer 3 has a smaller band gap than the p-type nitride semiconductor layer 2, the p-type impurity concentration of the p-type nitride semiconductor layer 2 and the p-type impurity concentration of the p-type nitride semiconductor layer 3 are both lower than the p-type impurity concentration of the p-type nitride semiconductor layer 1, and a method for producing same.

Nitride semiconductor light-emitting element and method for producing same

Disclosed is a nitride semiconductor light-emitting element comprising a p-type nitride semiconductor layer 1, a p-type nitride semiconductor layer 2, and a p-type nitride semiconductor layer 3 placed in order above a nitride semiconductor active layer, wherein the p-type nitride semiconductor layer 1 and p-type nitride semiconductor layer 2 each contain Al, the average Al composition of the p-type nitride semiconductor layer 1 is equivalent to the average Al composition of the p-type nitride semiconductor layer 2, the p-type nitride semiconductor layer 3 has a smaller band gap than the p-type nitride semiconductor layer 2, the p-type impurity concentration of the p-type nitride semiconductor layer 2 and the p-type impurity concentration of the p-type nitride semiconductor layer 3 are both lower than the p-type impurity concentration of the p-type nitride semiconductor layer 1, and a method for producing same.

A nitride semiconductor device is provided that prevents development of cracks, that has nitride semiconductor thin films with uniform thicknesses and good growth surface flatness, and is thus consistent in characteristics, and that can be fabricated at a satisfactory yield. In this nitride semiconductor device, the nitride semiconductor thin films are grown on a substrate having an off-angle between a direction normal to the surface of ridges and the crystal direction &#x3c;0001&#x3e;. This helps either reduce or intentionally promote diffusion or movement of the atoms or molecules of a source material of the nitride semiconductor thin films through migration thereof. As a result, a nitride semiconductor growth layer with good surface flatness can be formed, and thus a nitride semiconductor device with satisfactory characteristics can be obtained.

Nitride semiconductor device

On a processed substrate having an engraved region as a depressed portion formed thereon, a nitride semiconductor thin film is laid. The sectional area occupied by the nitride semiconductor thin film filling the depressed portion is 0.8 times the sectional area of the depressed portion or less.

Nitride semiconductor layers on substrate having ridge portions with inflow prevention walls near engraved regions

A nitride semiconductor laser device uses a substrate with low defect density, contains reduced strains inside a nitride semiconductor film, and thus offers a satisfactorily long useful life. On a GaN substrate () with a defect density as low as 10cmor less, a stripe-shaped depressed portion () is formed by etching. On this substrate (), a nitride semiconductor film () is grown, and a laser stripe () is formed off the area right above the depressed portion (). With this structure, the laser stripe () is free from strains, and the semiconductor laser device offers a long useful life. Moreover, the nitride semiconductor film () develops reduced cracks, resulting in a greatly increased yield rate.

Nitride semiconductor light-emitting device and method for fabrication thereof

An optical recording/reproducing apparatus is arranged so that, upon recording or reproducing a recording medium having a plurality of recording layers, the gap of the lens groups at the time of forming a converged light spot on this first recording layer is DIS (1), the gap of the lens groups at the time of forming the converged light spot on the N-th layer (the furthest layer from the surface of the recording medium) is DIS (N) and the neutral point of the spherical-aberration correcting mechanism is set at a position satisfying the following expression: lens group gap dst (3)=((DIS (1)+DIS (N))/2.

Optical recording/reproducing apparatus

Nitride semiconductor device with depressed portion

At the preceding stage of a first one of two APP decoders that constitute a turbo decoder, there is provided a logarithmic-likelihood computing circuit that creates and outputs logarithmic likelihoods L(y'|y) of a reproduced signal y&#x2032;which is soft information. The first APP decoder has an APP decoding function of receiving logarithmic likelihoods L(y&#x2032;|y) of the reproduced signal yas well as a priori information as to code data c&#x2032;, updating the code data c&#x2032;and producing outputs of a posteriori probabilities according to trellis diagram information that satisfy constraints concerning an RLL modulation. Turbo decoding becomes compatible with the RLL demodulation, and a turbo decoding with high error-correcting capability is usable in reproducing channel data arecorded onto a recording medium, which allows a recording density of the recording medium to be increased.

Decoding method and recording-medium reproducing apparatus

An RLL demodulator for performing RLL demodulation on primary modulation data performs hard demodulation outside an iterative decoding loop. Further, decoding in compliance with a constraint concerning a PR transfer characteristic is performed by a PR-channel APP detector which performs iterative decoding by repeatedly feeding and receiving a priori information regarding the primary modulation data to and from an APP decoder for error-correcting codes.

Recording-medium reproducing apparatus, decoding method, decoding program, and program-recorded medium

Method for fabrication of semiconductor device

At a preceding stage of a PR-channel APP decoder out of two APP decoders constituting a turbo decoder is disposed a logarithmic-likelihood computing circuit that computes logarithmic likelihoods L(y'|y) of a reproduced signal y&#x2032;, which is soft information. At a succeeding stage of the PR-channel APP decoder, on the other hand, a likelihood-transform RLL demodulator and a likelihood-transform RLL modulator capable of treating logarithmic likelihood ratios, which are soft information, are disposed between this APP decoder and a convolutional-code APP decoder. Thus, both RLL demodulation and turbo decoding can be fulfilled, and a turbo decoding of high error-correcting capability can be used to reproduce channel data arecorded on a recording medium. As a result, the recording density of the recording medium is enhanced.

Coding method, recording medium, decoding method, and recording-medium reproducing apparatus

An optical recording/reproducing apparatus is intended for a recording medium having at least two information recording layers. The apparatus has at least two lenses, a first lens and a second lens, for condensing a light beam to irradiate an information recording layer. The at least two lenses are designed such that a light beam condensed by these lenses upon an information recording layer closest to these lenses has a minimum spherical aberration.

Optical recording/reproducing apparatus for multi-layer recording media that alleviates adverse effect of spherical aberration beyond compensation by changing the numerical aperture of combined lenses

An optical recording/reproducing apparatus is arranged so that, upon recording or reproducing a recording medium having a plurality of recording layers, the gap of the lens groups at the time of forming a converged light spot on this first recording layer is DIS(), the gap of the lens groups at the time of forming the converged light spot on the N-th layer (the farthest layer from the surface of the recording medium) is DIS(N) and the neutral point of the spherical-aberration correcting mechanism is set at a position satisfying the following expression: lens group gap dst()=((DIS ()+DIS(N))/2.

An optical pickup device has a semiconductor laser for emitting a light beam, a hologram, a light-concentrating optical system, a collimation lens and a measuring unit for measuring quantity of light. The hologram generates a first light beam by splitting the light beam, which has passed through the light-concentrating optical system, along a first straight line that is perpendicular to the optical axis of the light beam and serves as a boundary, and then guides the light beam to the measuring unit. The measuring unit is provided with photosensors, which are provided linearly symmetrical each other with respect to an axis of symmetry of a straight line that extends through the optical axis of the first light beam and corresponds to the first straight line and arranged in positions located apart from the optical axis of the first light beam. An aberration signal is detected by a difference between electric signals from two of the photosensors. By measuring and correcting the spherical aberration of a light-concentrating optical system, the optical pickup device records and reproduces information on each information recording layer of a multi-layer optical disk even when a cover glass thickness error, a lens interval error and a lens thickness error exist.

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Tenri, Japan

Eiji Yamada