Nippon Telegraph and Telephone Corporation

Ntt Electronics Corporation

Mitsubishi Denki Kabushiki Kaisha

Yoshifumi Muramoto

Tadao Ishibashi

Seigo Ando

Masahiro Nada

Haruki Yokoyama

Fumito Nakajima

Hideaki Matsuzaki

Yoshiyuki Doi

Takaharu Ohyama

Yukihiro Hirota

Atsushi Kanda

Yoshiho Maeda

Kimikazu Sano

Toshihide Yoshimatsu

Kazutoshi Kato

Masahiro Yuda

Susumu Shimoyanagida

Atsuo Kozen

Osaake Nakajima

A light receiving element includes a first substrate, a photodiode formed on a main surface of the first substrate, and a second substrate constituted by a semiconductor and adhered to a rear surface side of the first substrate by an adhesive layer formed from a resin adhesive. A light receiving element according to an embodiment includes a lens that is formed on the side of an adhesion surface of the second substrate, has a convex surface, and is disposed in a light receiving region of the photodiode. The light receiving side of the photodiode is oriented toward the side of the first substrate. The lens is disposed so that the convex surface thereof is oriented toward the side of a light receiving surface of the photodiode.

Light-receiving element and method for manufacturing element

An optical waveguide integrated light receiving element includes an optical waveguide () arranged on a side of a second contact layer () opposite to a side where a light absorption layer () is arranged, having a waveguide direction parallel to a plane of the light absorption layer (), and optically coupled with the second contact layer (). The second contact layer () has, in a planar view, a size of an area smaller than that of the light absorption layer () and arranged inside the light absorption layer ().

Optical waveguide integrated light receiving element and method of manufacturing the same

To obtain high linearity without sacrificing light-receiving sensitivity and a high speed, an avalanche photodiode includes an avalanche layer () formed on a first light absorption layer (), an n-field control layer () formed on the avalanche layer (), and a second light absorption layer () formed on the field control layer (). If a reverse bias voltage is applied, a donor impurity in the field control layer () ionizes, and a high electric field is induced in the avalanche layer (). The n-type doping amount in the field control layer () is set such that the impurity concentration in the second light absorption layer () sufficiently depletes at the time of reverse bias application.

Avalanche photodiode

An APD is provided with the semi-insulating substrate, a first mesa having a first laminate constitution in which a p-type electrode layer, a p-type light absorbing layer, a light absorbing layer with a low impurity concentration, a band gap inclined layer, a p-type electric field control layer, an avalanche multiplier layer, an n-type electric field control layer, and an electron transit layer with a low impurity concentration are stacked in this order on a surface of the semi-insulating substrate, a second mesa having an outer circumference provided inside an outer circumference of the first mesa as viewed from the laminating direction and having a second laminate constitution in which an n-type electrode buffer layer and an n-type electrode layer are stacked in this order on a surface on the electron transit layer side, and a depletion control region that is provided in layers on the second mesa side relative to the p-type electric field control layer, formed in an encircling portion provided inside an outer circumference of the first mesa and encircling an outer circumference of the second mesa, and prevents the encircling portion of the p-type electric field control layer from being depleted when bias is applied.

The present invention is intended to provide a compact and simple optical semiconductor device that reduces crosstalk (leakage current) between light receiving elements. According to the present invention, since a back surface electrode is a mirror-like thin film, crosstalk to an adjacent light receiving element can be suppressed, thereby reducing a detection error of a light intensity. By disposing a patterned back surface electrode or by disposing an ohmic electrode at the bottom of an insulating film over the whole back surface, contact resistance on the back surface can be reduced. By using the optical semiconductor elements with a two-dimensional arrangement and by using a mirror-like thin film as the back surface electrode, crosstalk can be reduced. By accommodating the optical semiconductor elements in the housing in a highly hermetic condition, the optical semiconductor elements can be protected from an external environment.

Optical semiconductor device

A layer in which the potential level difference normally unrequired for device operation is generated is positively inserted in a device structure. The potential level difference has such a function that even if a semiconductor having a small bandgap is exposed on a mesa side surface, a potential drop amount of the portion is suppressed, and a leakage current inconvenient for device operation can be reduced. This effect can be commonly obtained for a heterostructure bipolar transistor, a photodiode, an electroabsorption modulator, and so on. In the photodiode, since the leakage current is alleviated, the device size can be reduced, so that in addition to improvement of operating speed with a reduction in series resistance, it is advantageous that the device can be densely disposed in an array.

Semiconductor device

An APD is provided with a semi-insulating substrate, a first mesa having a first laminate constitution in which a p-type electrode layer, a p-type light absorbing layer, a light absorbing layer with a low impurity concentration, a band gap inclined layer, a p-type electric field control layer, an avalanche multiplier layer, an n-type electric field control layer, and an electron transit layer with a low impurity concentration are stacked in this order on a surface of the semi-insulating substrate, a second mesa having an outer circumference provided inside an outer circumference of the first mesa as viewed from the laminating direction and having a second laminate constitution in which an n-type electrode buffer layer and an n-type electrode layer are stacked in this order on a surface on the electron transit layer side of the first mesa, and in the APD, a total donor concentration of the n-type electric field control layer is lower than a total acceptor concentration of the p-type electric field control layer in a range of 2&#xd7;10to 1&#xd7;10/cm.

An electron injected APD with an embedded n electrode structure in which edge breakdown can be suppressed without controlling the doping profile of an n-type region of the embedded n electrode structure with high precision. The APD comprising a buffer layer with a low ionization rate is inserted between an n electrode connecting layer and an avalanche multiplication layer. Specifically, the APD is an electron injected APD in which an n electrode layer, the n electrode connecting layer, the buffer layer, the avalanche multiplication layer, an electric field control layer, a band gap gradient layer, a low-concentration light absorbing layer, a p-type light absorbing layer, and a p electrode layer are sequentially stacked, and a light absorbing portion that includes at least the low-concentration light absorbing layer and the p-type light absorbing layer forms a mesa shape.

In an electron-injection type APD, it is necessary to prevent a dark current increase and to secure the life time of the device. It is demanded to improve reliability of the APD with a lower production cost. With the InP buffer layer having an n-type doping region on the inside of a region defined by an optical absorption layer, a predetermined doping profile is achieved by ion implantation. Thus, electric field concentration in the avalanche multiplication layer is relaxed. Furthermore, a low-concentration second optical absorption layer is provided between the optical absorption layer and the avalanche multiplication layer. Responsivity of the optical absorption layer is maximized, and depletion of the lateral surface of the optical absorption layer is prevented; thus, electric field concentration is prevented. Preventing edge breakdown, the device improves its reliability.

Avalanche photodiode having doping region with monotonically increasing concentration distribution

A photodiode has an optical absorption layer composed of a depleted first semiconductor optical absorption layer with a layer width Wand a p-type neutral second semiconductor optical absorption layer with a layer width W. The ratio between Wand Wis set such that the total carrier transit time &#x3c4;becomes minimum in the optical absorption layer. The photodiode can further include a depleted semiconductor optical transmission layer with a bandgap greater than that of the first semiconductor optical absorption layer, between the first semiconductor optical absorption layer and an n-type semiconductor electrode layer.

Photodiode

This semiconductor photodetector includes a photoabsorption layer, an n-type first semiconductor layer, and a p-type second semiconductor layer. The photoabsorption layer comprises an n-type first layer and a p-type second layer formed in contact with the first layer. The first semiconductor layer is arranged on the side of the first layer and has a shorter wavelength at a light absorption edge and a lower refractive index than in the photoabsorption layer. The second semiconductor layer is arranged on the side of the second layer and has a shorter wavelength at a light absorption edge and a lower refractive index than in the photoabsorption layer. When a predetermined reverse bias voltage is applied between the first and second semiconductor layers, the first layer is entirely depleted and the second layer is partially depleted.

Semiconductor photodetector

Apparatus and method which commands the displaying of audio information on a television receiver display in the case where it is judged that a sound muting control unit was operated, whereby the audio information is displayed by a single operation of the sound muting control unit.

Apparatus and method for controlling the muting of sound and the display

A television receiver includes a closed-caption signal demodulator, an existence-of-closed-caption-signal discriminator located upstream of the demodulator, and a character memory for supplying a simple character, meaning that a closed-caption signal exists in an image signal, onto the screen of the television receiver. This simple character is supplied to the screen upon receipt of a discrimination signal, indicating that a closed-caption signal, exists in an image signal from the existence-of-closed-caption-signal discriminator. With this television receiver, the user can recognize, at a time prior to actual selection of closed-caption signal demodulation, whether or not a closed-caption signal exists, in an image signal.

Growing community of inventors

Atsugi, Japan

Yoshifumi Muramoto