下村 和彦

Current-injected light emission was confirmed for metal organic vapor phase epitaxy (MOVPE) grown (Ga)InAs/InP quantum dots (QDs) on directly bonded InP/Si substrate. The InP/Si substrate was prepared by directly bonding of InP thin film and a Si substrate using a wet-etching and annealing process. A p-i-n LED structure including Stranski-Krastanov (Ga) InAs/InP QDs was grown by MOVPE on an InP/Si substrate. No debonding between Si substrate and InP layer was observed, even after MOVPE growth and operation of the device under continuous wave conditions at RT. The photoluminescence, current/voltage, and electroluminescence characteristics of the device grown on the InP/Si substrate were compared with reference grown on an InP substrate. (C) 2015 The Japan Society of Applied Physics

InP nanowires were successfully grown on an InP(111)B substrate by low pressure metal organic vapor phase epitaxy (MOVPE) using an indium catalyst. The self-catalytic vapor-liquid-solid (VLS) mode was used to obtain high quality nanowires where a deposited indium droplet acts as the catalyst instead of a metal particle, as with the conventional VLS mode. The nanowire characteristics are discussed as a function of the preheating and growth temperatures used with this method InP nanowires vertically aligned on (111) orientation were obtained and the nanowire density was dependent on the preheating temperature, while the total growth volume was mainly dependent on the growth temperature. From these results, the optimal growth conditions to produce InP nanowires with small diameter, high density, and lower dispersion have been determined. (C) 2014 Elsevier B.V. All rights reserved.

GaInAs/InP multi quantum wells light-emitting diode, emitting at 1.3-mu m, was fabricated by metal organic vapor phase epitaxi on wafer bonded InP/Quartz substrate. The device has been operated under continuous wave operation at room temperature.

The surface conditions of thin film InP epitaxial layers transferred to a Si substrate have been investigated in terms of void size, density, and area occupied by the voids, by changing the annealing temperature and ramping periods to reach the annealing temperature of 400 degrees C. Through a long ramp annealing time of 45 h, the voids generated were downsized by up to two orders of magnitude, and the total number of voids also greatly decreased compared that for the typical annealing process at 400 degrees C. This resulted in a reduction of the InP surface area occupied by voids from 3.96 to 0.03%. Then, successful fabrication of void-free 50 mm InP/Si substrates without forming any outgassing channels has been I demonstrated. (C) 2014 The Japan Society of Applied Physics

The surface conditions of thin film InP epitaxial layers transferred to a Si substrate have been investigated in terms of void size, density, and area occupied by the voids, by changing the annealing temperature and ramping periods to reach the annealing temperature of 400 °C. Through a long ramp annealing time of 45 h, the voids generated were downsized by up to two orders of magnitude, and the total number of voids also greatly decreased compared that for the typical annealing process at 400 °C. This resulted in a reduction of the InP surface area occupied by voids from 3.96 to 0.03%. Then, successful fabrication of void-free 50 mm InP/Si substrates without forming any outgassing channels has been demonstrated.

We report here on the successful transfer of thin film InP epi-layer onto Si substrate using wafer direct bonding technique, to be used as a platform of GaInAsP system growth. Our approach is promising in terms of high density integration of InP-based several functional devices on Si substrate.

We have developed an ultrathin InP template with low defect density on SiO2-Si and glass substrate by employing wet etching and wafer direct bonding technique. We have demonstrated epitaxial growth on these substrates and GaInAs/InP multiple quantum well layers were grown by low pressure metal-organic vapor-phase epitaxy. Photoluminescence measurements of the layers show that they are optically active and we have obtained almost the same intensity from these substrates compared to the InP substrate. These results may be attributed to improvement of InP template quality and should provide further improvements in device performance realized on SiO2-Si and glass substrate. And, these are promising results in terms of integration of InP-based several functional optical devices on SiO2-Si and glass substrate. © 2013 WILEY-VCH Verlag GmbH &amp Co. KGaA, Weinheim.

Au-assisted growth of InAs NWs by MOVPE growth was investigated. We will discuss the NWs characteristics on GaAs and InP substrate with (111)B and (100) orientation, and on the V/III ratio during the growth. We have observed the growth direction of NWs on each substrates and confirmed that the surface diffusion have relation to the diameter of NWs. In the GaAs (111)B substrate, the diameter and length of NWs were depended on the local density of NWs. Furthermore, the tapered NWs were decreased by lowering the V/III ratio. © 2013 WILEY-VCH Verlag GmbH &amp Co. KGaA, Weinheim.

We have investigated the current injected spectrum of flat-topped LED using self-assembled Stranski-Krastanov (S-K) InAs/InP quantum dots (QDs) grown by selective area low pressure metalorganic vapor phase epitaxy and a double-capping procedure. Selective area growth using an SiO2 mask with narrow stripes was carried out to tailor a wide emission range for the QDs in sixteen arrayed waveguides. Each waveguide core contained three stacked QD layers with different QD heights and Ga content in the GaInAs buffer layer. We have measured the spectrum change of current injection, and have estimated the intensity variation in each QDs layer. By increasing the FCL thickness of three QDs layers, output intensity of each layer has become equal, and we have obtained more than 500 nm spectrum width with flat-topped spectrum shape. (C) 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

We have developed an ultrathin InP template with low defect density on SiO2-Si and glass substrate by employing wet etching and wafer direct bonding technique. We have demonstrated epitaxial growth on these substrates and GaInAs/InP multiple quantum well layers were grown by low pressure metal-organic vapor-phase epitaxy. Photoluminescence measurements of the layers show that they are optically active and we have obtained almost the same intensity from these substrates compared to the InP substrate. These results may be attributed to improvement of InP template quality and should provide further improvements in device performance realized on SiO2-Si and glass substrate. And, these are promising results in terms of integration of InP-based several functional optical devices on SiO2-Si and glass substrate. (C) 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

InP/Si substrate has been fabricated by employing wet-etching and wafer direct bonding technique. The surface of the InP/Si substrate was very smooth and no strain was observed. On top of the substrate, InAs/InP quantum dots (QDs) have been monolithically grown using metal organic vapor phase epitaxy (MOVPE). According to photo-luminescence (PL) measurement, almost the same intensity, peak wavelength and full width half of maximum (FWHM) have been observed compared to QDs on InP substrate. © 2013 IEEE.

We have obtained the wide energy level control of InAs QDs structure where the PL peak wavelength were ranged from 1200nm to 1800nm. Stranski - Krastanov InAs QDs were grown by low pressure all metal-organic source MOVPE. We have controlled the InAs QDs energy level by changing the buffer layer composition under the QDs and the height using double-capping procedure and also supply amount of QDs.

An ultrathin InP template with extremely low defect density was realized on Si substrate using wet etching and wafer direct bonding technique. On top of the InP/Si substrate, asymmetric SiO2 mask pattern on one side of the arrayed waveguides was prepared and selective metal-organic vapor-phase epitaxy (MOVPE) growth has been demonstrated. According to the cross-sectional scanning electron micrograph (SEM) images, gradually varied height of GaInAs/InP multiple quantum well (MQW) structures were realized on the substrate and photoluminescence (PL) measurement showed different band-gaps of the MQW structures. Our approach is of importance to control the in-plane band-gap energy for the integration of InP-based various functional devices on Si substrate.

Flat-topped emission with a spectral width greater than 500 nm was obtained from self-assembled Stranski-Krastanov (SK) InAs/InP quantum dots (QDs) grown by selective area low-pressure metal organic vapor phase epitaxy using a double-capping procedure. Selective area growth using an SiO2 mask with narrow stripes was carried out to tailor a wide emission range for the QDs in sixteen arrayed waveguides. Each waveguide core contained three stacked QD layers with different QD heights and Ga content in the GaInAs buffer layer. An investigation was carried out into the optimum Ga content and QD height for increasing the emission intensity and obtaining equal intensity from each QD layer. (C) 2012 The Japan Society of Applied Physics

Wavelength demultiplexed light switching is numerically calculated in the variable index arrayed waveguide. Wavelength demultiplexed light is switched in 4 output ports by changing the refractive index of variable index arrayed waveguide with 16 array waveguides. In the calculation, the phase differences in each arrayed waveguide, and the diffraction in the star coupler are considered. In 4 output ports switching, numerically calculated the refractive index changes of 16 array waveguides are numerically calculated to obtain the 24 switching pattern, and also calculated the crosstalk of each switching.

We have demonstrated switching characteristics in a wavelength switch based on multiple GaInAs/InP quantum wells. It consisted of straight arrayed waveguides with a linearly varying refractive index distribution. The refractive index can be changed via the thermo-optic (TO) effect. Using a Ti/Au thin-film heater to generate the TO effect, we realized four-port switching at four demultiplexed wavelengths. In addition, by changing the structure of the heater from rectangular to triangular, the power consumption for four-port switching was reduced by half.

我々はMOVPE選択成長InAs量子ドットを用いたアレイ型広帯域LEDの作製を行っている.ダブルキャップ法を用いた量子ドットの高さ制御とバッファ層組成制御によって,層ごとに量子ドット準位を変えることで発光波長の広帯域化を行っている.今回,量子ドット高さ,バッファ層組成を変更した数パターンの3層LEDについてスペクトル解析を行ったので報告する.

More than 400nm broadband luminescence was obtained from 3 layered InAs/InP QDs array waveguides. InAs QDs were grown by Stranski-Krastanov grown mode using selective MOVPE growth and double cap procedure. The selective MOVPE was performed using 16 stripe mask array with a wide mask at one side of the array. The heights of the QDs were controlled vertically by changing the first-cap layer thickness during the double-cap procedure. Furthermore, we have tried to control the emission energy of QDs by changing the Ga composition of Ga xIn 1-xAs buffer layer under the QDs. By using these techniques, we have fabricated the broadband emission devices. © 2012 WILEY-VCH Verlag GmbH &amp Co. KGaA, Weinheim.

More than 400nm broadband luminescence was obtained from 3 layered InAs/InP QDs array waveguides. InAs QDs were grown by Stranski-Krastanov grown mode using selective MOVPE growth and double cap procedure. The selective MOVPE was performed using 16 stripe mask array with a wide mask at one side of the array. The heights of the QDs were controlled vertically by changing the first-cap layer thickness during the double-cap procedure. Furthermore, we have tried to control the emission energy of QDs by changing the Ga composition of GaxIn1-xAs buffer layer under the QDs. By using these techniques, we have fabricated the broadband emission devices. (C) 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

我々はGaInAs/InP MQWコア構造を用いたアレイ導波路型波長スイッチの研究を行っている.アレイ導波路はMOVPE選択成長法を用いてMQW層厚を徐々に変化させ,各導波路において屈折率分布を有する構造となっている.これまでにも,大きな屈折率変化が期待できる熱光学効果による波長スイッチを作製し,スイッチング特性を示した.今回,Ti/Auヒータを三角形状に作製し,消費電力の低減と4波長でのポート間スイッチング動作を達成したので報告する.

Broadband spectrum emission was obtained for self-assembled Stranski-Krastanov (S-K) InAs/InP quantum dots (QDs) grown by selective area low pressure metalorganic vapor phase epitaxy (MOVPE) using the double-cap procedure. Selective area growth using a SiO(2) narrow stripe mask array pattern was carried out to control and widen the emission wavelength range of the QDs in 16 stripe mask array waveguides. The height of the QDs in the multi stacked QD layers was changed using the double-cap procedure, and the strain was controlled by changing the composition of the GaInAs buffer layer under the QDs, which resulted in the broadband spectrum emission of this structure. (C) 2010 Elsevier B.V. All rights reserved.

我々はGaInAs/InP MQW構造を用いたアレイ導波路型波長選択スイッチの研究を行っている.アレイ導波路は,MOVPE選択成長法において非対称SiO_2マスクパターンを用いることによりMQW層厚を徐々に変化させることで,それぞれのアレイ導波路に異なる屈折率を与えており,その分布は階段状となっている.この構造により,アレイ導波路を伝搬する光はそれぞれ異なる位相で出射して,スラブ導波路にて干渉し波面の揃う方向に回折する.また,回折角は波長に依存するので,波長の異なる光の集光する位置はそれぞれ異なり,異なる波長信号を別々のポートに取り出すことが可能となる.すなわち,これにより直線型アレイ導波路構造の波長分波器が実現できる.今回,Fortranを用いたシミュレーションにより,ローランド円構造に基づいたスラブ導波路における光の回折を考慮した波長分波特性,及びスイッチング特性の数値解析を行ったので報告する。

InAs/InP QDs broadband LED more than 450 nm spectrum width was successfully demonstrated. The broadband spectrum was obtained from the height controlled double-cap procedure and strain controlled buffer layer fabricated by the selective MOVPE technique.

We have demonstrated a carrier-injection-type wavelength switch composed of the straight waveguide array using GaInAs/InP MQW with linearly varying refractive index distribution fabricated by selective MOVPE.

Wavelength switching in the index-varied array waveguide is calculated. The device consists of waveguide array in which the refractive index varies gradually across the array and star coupler. In the calculation, the phase differences in each array waveguide, and the diffraction in the star coupler are considered. Refractive index distribution of the array waveguide for wavelength demultiplexing, and index change for switching are obtained.

We have demonstrated wavelength selective switching in the variable index arrayed waveguides using Ti/Au thin film.

キャリアを0次元に閉じ込める構造を持つ量子ドットは独特な特性を持つとされている.そして量子ドットはレーザやLEDのような様々な半導体光デバイスの性能を向上すると考えられている.量子井戸構造をでは高さ方向の一次元でのみエネルギー準位を制御可能であるが,一方で量子ドットでは三次元的な制御が可能であり,より広い範囲の波長制御が可能である.このことから広帯域な波長を放出する光源は1.55μm通信波長帯域を含む波長分割多重(WDM)や2.0μm付近の環境ガスセンサ,光干渉断層計などで応用可能である.今回の研究では,MOVPE選択成長法とダブルキャップ法による量子ドットアレイ構造を用いた400nmを超える量子ドットLEDの広帯域なEL発光特性を示す.

我々はGaInAs/InP MQW構造を用いたアレイ導波路型波長選択スイッチの研究を行っている.アレイ導波路は,MOVPE選択成長法において非対称SiO_2マスクパターンを用いることによりMQW層厚を徐々に変化させることで,それぞれのアレイ導波路に異なる屈折率を与えており,その分布は階段状となっている.この構造により,アレイ導波路を伝搬する光はそれぞれ異なる位相で出射して,スラブ導波路にて干渉し波面の揃う方向に回折する.また,回折角は波長に依存するので,波長の異なる光の集光する位置はそれぞれ異なり,異なる波長信号を別々のポートに取り出すことが可能となる.すなわち,これにより直線型アレイ導波路構造の波長分波器が実現できる.今回,BPMを用いたシミュレーションによりスラブ導波路構造を改善し,波長依存性の少ないプラズマ効果による波長選択スイッチを作製し,出射ポートの強度変化を観測できたので報告する.

我々はGaInAs/InP MQW構造を用いたアレイ導波路型波長選択スイッチの研究を行っている.アレイ導波路は,MOVPE選択成長法において非対称SiO_2マスクパターンを用いることによりMQW層厚を徐々に変化させ,導波路の屈折率が階段状に変化した構造となっており,これにより直線型アレイ導波路構造の波長分波器が実現できる.今回,大きな屈折率変化を期待することができる熱光学効果を用いて,GaInAs/InP MQW屈折率分布アレイ導波路型波長選択スイッチを作製し,4波長の波長分波特性および波長選択スイッチング特性が得られたので報告する.

Wavelength selective switch using GaInAs/InP MQW variable index arrayed waveguides have successfully demonstrated. The demultiplexed wavelength light could be exchanged the output ports by changing the refractive index of arrayed waveguides by using thermo-optic effect. (C) 2009 Optical Society of America

More than 400nm spectrum width LED was obtained in the In As QDs array waveguide using height changed QDs during double-cap procedure and strain controlled buffer in 3 layered QDs.

Four wavelength switching was successfully demonstrated in the wavelength selective switch using GaInAs/InP MQW variable index arrayed waveguide by thermo-optic (TO) effect. Four wavelength lights were switched and demultiplexed between the four output ports.

We have obtained the structual dependence on the performance of wavelength demultiplexing and switching in the variable refractive-index waveguide array using BPM simulation, and we have experimentally examined the improvement of crosstalk in this device.