Takaya Yamamoto

Bio: Takaya Yamamoto is an academic researcher. The author has contributed to research in topics: Avalanche photodiode & Semiconductor. The author has an hindex of 10, co-authored 23 publications receiving 277 citations.

Zn‐diffused In0.53Ga0.47As/InP avalanche photodetector

Abstract: Mesa In0.53Ga0.47As avalanche photodetectors were successfully fabricated by liquid‐phase‐epitaxial growth on (100) ‐InP substrate and Zn‐diffusion technique. An avalanche multiplication M as high as 32 was measured under broad‐area illumination provided by a cw InGaAsP laser at 1.3 μm. Distribution of M was measured by an electron‐beam‐induced current image of a scanning electron microscope, and uniform multiplication profiles were observed up to M=3 and M=12 at the mesa diameter of 300 and 150 μm, respectively.

Semiconductor laser element

Abstract: PURPOSE:To obtain stable lateral basic mode oscillation of a double hetero construction laser by forming projected stripes on the clad layer on an acitive layer. CONSTITUTION:An n-type InP clad layer 15, a non-doped In1-XGaXAsP1-Y active layer 16, and a p-type InP clad layer 17 are sequentially formed on an n-type InP substrate 14. A projected stripe 31 is formed in a plane parallel with the end surfaces 30, 30a on the layer 17, and the end surfaces 30, 30a are so etched as to form vertical stripes. An n-type In1-XGaXAsYP1-Y layer 18 is grown on the etched portion, and an ohmic electrode 7 is evaporated thereon. Thus, refractive index difference occurs laterally on the active layer 16 in the vicinity of the stripe 31 to effectively enclose the light to thus obtain stable lateral basic mode oscillation of a double hetero construction laser.

Room temperature c.w. operation of InGaAsP/InP heterostructure lasers emitting at 1.56 μm

Abstract: Room-temperature c.w. operation of InGaAsP/InP heterostructure lasers grown by liquid-phase epitaxy was achieved at 1.56 μm. An active InGaAsP layer was essentially sandwiched by InP, though a thin InGaAsP buffer layer was deposited to prevent the melt-back of the active layer. Threshold current was typically 300 mA for a 17 μm wide oxide-defined stripe laser.

Ac generator for vehicle

Abstract: In An AC generator for a vehicle in which a bearing is inserted into a bearing box formed in a bracket and the bearing is fixed and retained by a retainer, the retainer has a cylindrical shape and a threaded portion is formed on the cylindrical section thereof, a threaded portion is formed on the bearing box, and the threaded portion of the retainer is directly screwed to the threaded portion of the bearing box in order to fix and retain the bearing, so that the gap between the outer circumference surface of the bearing box or the outer circumference surface of the retainer and the opposing side of a cooling fan is made uniform.

Semiconductor Light Emitting Device

Abstract: The present disclosure relates to a semiconductor light emitting device, comprising: a plurality of semiconductor layers, including a first semiconductor layer having a first conductivity, a second semiconductor layer having a second conductivity different from the first conductivity, and an active layer interposed between the first semiconductor layer and the second semiconductor layer, generating light via electron-hole recombination; a first electrode, supplying either electrons or holes to the plurality of semiconductor layers; a second electrode, supplying, to the plurality of semiconductor layers, electrons if the holes are supplied by the first electrode, or holes if the electrons are supplied by the first electrode; a non-conductive distributed bragg reflector coupled to the plurality of semiconductor layers, reflecting the light from the active layer; and a first light-transmitting film coupled to the distributed bragg reflector from a side opposite to the plurality of semiconductor layers with respect to the non-conductive distributed bragg reflector, with the first light-transmitting film having a refractive index lower than an effective refractive index of the distributed bragg reflector.

Light Emitting Device

Abstract: By doping an organic compound functioning as an electron donor (hereinafter referred to as donor molecules) into an organic compound layer contacting a cathode, donor levels can be formed between respective LUMO (lowest unoccupied molecular orbital) levels between the cathode and the organic compound layer, and therefore electrons can be injected from the cathode, and transmission of the injected electrons can be performed with good efficiency. Further, there are no problems such as excessive energy loss, deterioration of the organic compound layer itself, and the like accompanying electron movement, and therefore an increase in the electron injecting characteristics and a decrease in the driver voltage can both be achieved without depending on the work function of the cathode material.

Semiconductor light emitting element

Abstract: The present disclosure relates to a semiconductor light-emitting element, which comprises: a first light-emitting part, a second light-emitting part, and a third light-emitting part, wherein each of the light-emitting parts includes multiple semiconductor layers including a first semiconductor layer, an active layer, and a second semiconductor layer, laminated in sequence, the first semiconductor layer having a first conductivity, the active layer generating light through the recombination of an electron and a hole, and the second semiconductor layer having a second conductivity different from the first conductivity; a non-conductive reflecting film which is formed to cover the multiple semiconductor layers and reflects light generated from the active layer; a first electrode which is provided to electrically communicate with the first semiconductor layer of the first light-emitting part and which supplies one of an electron and a hole; a second electrode which is provided to electrically communicate with the second semiconductor layer of the second light-emitting part and which supplies the other of the electron and the hole; and an auxiliary pad formed on the non-conductive reflecting film which covers the third light-emitting part.

In0.53Ga0.47As photodiodes with dark current limited by generation‐recombination and tunneling

Abstract: We report on low‐dark‐current IN0.53GA0.47As photodiodes in which generation‐recombination current dominates diode leakage up to as high as 100 V. At higher voltages, tunneling currents become dominant, resulting in the soft breakdown characteristic widely observed in these materials. The dark current versus voltage characteristics have been fit to variations in current of over six orders of magnitude and a temperature range greater than 150 K using a theory which includes generation‐recombination, tunneling, and shunt components.