Hitachi, Ltd.

Takeshi Kitatani

Masahiko Kondow

Toshiaki Tanaka

Yoshiaki Yazawa

Terunori Warabisako

Akira Sato

Makoto Kudo

Junko Minemura

In a semiconductor laser for emitting light perpendicular to substrate crystal, including, on the substrate crystal, an active layer for generating light, a cavity structure sandwiching the active layer by reflecting mirrors so as to obtain a laser beam from the light generated from the active layer, and a regrown semiconductor layer between the active layer and one of the reflecting mirrors, a regrown interface or a face very close to the regrown interface is formed by a thin film containing dopants of high concentration. With the configuration, an adverse influence of a contamination deposit on the regrown interface is eliminated by delta-doping the regrown interface. The cost is reduced and device resistance is also reduced to 50 &OHgr; or less. Thus, an edge emitting laser (VCSEL) for realizing a optical module achieving a high speed characteristic over 10 Gb/s is obtained.

Semiconductor laser, ray module using the same and ray communication system

A surface emitting laser device comprising, on a semiconductor substrate, an active region for generating light, a current confinement region disposed on the side opposite to the semiconductor substrate relative to the active region, an optical cavity comprising reflectors putting the active region and the current confinement region vertically therebetween in the direction of layering the semiconductor layer, a first electrode disposed on the side of the semiconductor substrate relative to the current confinement region and a second electrode disposed on the side opposite to the semiconductor layer relative to the current confinement region, and having a layered structure capable of forming 2-dimensional carriers between the current confinement region and the second electrode, in which a current flowing from the electrode to the current confinement region has a component in the horizontal direction relative to the surface of the substrate and is conducted mainly by way of the channel for the 2-dimensional carrier gas, whereby the device resistance can be reduced greatly to provide high speed optical module using the surface emitting laser improved in the performance operating at a high speed of 10 Gb/s or more.

Vertical cavity surface emitting lasers, optical modules and systems

A light receiving element having excellent characteristics, including high sensitivity and high response speed, can be achieved by a light element comprising unit structures each having two pn junction semiconductor layers, and a lightly doped semiconductor layer having low impurity density, lower than those of the p-type regions and the n-type regions of the two pn junction semiconductor layers, and which is sandwiched between the two pn junction semiconductor layers. The p-type regions of the pn junction semiconductor layers are disposed opposite to each other on opposite sides of the lightly doped semiconductor layer, respectively, and the n-type regions of the pn junction semiconductor layers are disposed opposite to each other on the opposite sides of the lightly doped semiconductor layer, respectively. In a method of fabricating such a light receiving element, using controlled shutters or an ion beam apparatus, the layers are formed of optimum semiconductors, in an optimum thickness and in optimum impurity densities. In this structure, photogenerated carriers move mainly through the lightly doped semiconductor layer. Therefore, the lifetime of the carriers is increased, and the drift mobility of the carriers is enhanced, so that the light receiving element is able to function with a high sensitivity at a high response speed.

Light receiving element and a method of fabricating the same

Growing community of inventors

Hachioji, Japan

Takeshi Kitatani