下村 和彦

Novel ZnCdSe/BeZnTe type-II superlattices (SLs) are very attractive For active layers of new visible light emitting devices using II-VI compounds on InP substrates. It is expected that the transition energy of the SL can be controlled in a wide visible range from 761 to 397 nut by only changing layer-thickness combinations. In this study, the ZnCdSe/BeZnTe SLs grown on InP substrates by molecular beam epitaxy with the shutter Control method for the first time. In the X-ray diffraction measurements, sharp satellite peaks from the SL structures could be observed, which indicates that high crystal qualities and steep interfaces between ZnCdSe and BeZnTe layers were obtained by using the shutter control method. For the SL samples with several layer-thickness combinations, wide-range visible emissions from 740 to 507 nut could be observed in the Pl measurements at 15 K. The PL peaks are comparable to theoretical transition energies calculated for ZnCdSe/BeZnTe SL structures. A double hetero (DH) structure consisting of ZnCdSe/BeZnTe SLs and BeZnTe cladding layers was fabricated. In the PL spectrum of the DH sample at 15 K. sharp peak emissions at 517 and 614 nm could be observed.

ZnCdSe/BeZnTe II-VI compound superlattices (SLs) were grown on InP substrates by molecular beam epitaxy for the first time. In the X-ray diffraction studies, definite satellite Peaks were observed for each sample, which indicates that fine periodic SL structures were obtained. For SL samples with several layer thickness combinations, wide-range visible emissions from 740 to 507 nm were observed during photoluminescence (PL) studies at 15 K. Comparison of PL emission properties at 15 K for a ZnCdSe/BeZnTe SL and ZnCdSe bulk samples showed the superior emission intensity of the SL sample, A double hetero-structure (DH) consisting of ZnCdSe/BeZnTe SLs and BeZnTe cladding layers was fabricated. In the PL spectrum of the DH sample at 15 K, sharp emission peaks at 517 and 604 nm were observed. Visible light emitting diodes were fabricated by applying ZnCdSe/BeZnTe SLs as the active layer, and were evaluated under pulsed current injections at room temperature. A single-peak yellow-green emission around 562 nm was obtained.

BeZnCdSe quaternaries, MgSe/BeZnCdSe superlattice (SL) and BeZnCdSe quantum well (QW) structures were grown on InP substrates by molecular beam epitaxy for the first time. As for a lattice-matched Be-0.08(Zn0.30Cd0.70)(0.92)Se sample, a single-peak photoluminescence (PL) spectrum was observed at the temperature range from 15K to room temperature. The PL peak wavelength and the full-width at half-maximum (FWHM) value at 15 K were 572 nm and 8.8 meV, respectively. PL measurements of MgSe/BeZnCdSe SL samples were observed single-peak emissions in the green-to-blue color range from 525 to 470 nm at 15 K with changing MgSe layer-thickness ratio from 0.20 to 0.60. As for the QW sample consisting of four BeZnCdSe QWs with a different well width, PL peaks corresponding to each QW were observed in the wavelength range from 459 to 561 nm at 15 E(. By fitting calculated transition energies in the QWs to the PL peak energies. the band offset ratio between the BeZnCdSe well and the MgSe/BeZnCdSe SL barrier was estimated to be DeltaE(c) : DeltaE(v) = 9 : 1. (C) 2001 Elsevier Science B.V. All rights reserved.

我々は、MOVPE選択成長により異なる屈折率を有するアレイ導波路を用いた光偏向器を提案した。これはアレイ導波路の両側に非対称な幅を持つガラスマスクを配置することによって、アレイ導波路の層厚を変化し、光導波に伴う位相変化を各導波路において変え、光偏向を行う素子である。この素子において、アレイ導波路への光分配を行うために多モード干渉(MMI)結合器の設計および試作を行った。理論的には、16分岐MMIにおいて出射光のばらつきは、0.42dBと推定された。実際にGaInAs/InP MQW導波路を用いて作製した16分MMIにおいては波長1.56μm光において、出射光のばらつきは0.88dBであった。また、この素子を波長分割素子へ応用するために分割波長間隔等の数値計算を行った。

We report the wavelength control of the arrayed waveguide using MOVPE selective area growth. The asymmetric mask pattern, which placed the wide mask next to the one-side-arrayed waveguide, resulted in the gradient change of the bandgap wavelength in array waveguides. The wavelength in each waveguide was found to be linearly changed and clearly dependent on the wide mask width W-w. A 100nm photoluminescence peak wavelength shift in the arrayed waveguide was achieved for a 50 mum asymmetric mask pattern, while maintaining linearly shifted profiles. (C) 2000 Elsevier Science B.V. All rights reserved.

BeZnTe II-VI compound ternary alloys with various Be composition (x(Be)) were grown on InP substrates by molecular beam epitaxy. From absorption coefficient measurements at room temperature. the bandgap energies (E-g) were evaluated as a function of x(Be). The bandgap energy monotonically increases from 2.24 to 3.29 eV when increasing x(Be) from 0 to 0.62 By fitting a quadratic equation in terms of x(Be) to the E-g values, E-g = 2.24(1 - x(Be)) + 4.1x(Be) + 0.1x(Be)(x(Be) - 1) is obtained, and tho bowing parameter is seen to be as small as 0.1eV. Thus, the E-g value of BeZnTe, when the lattice constant is matched to InP, is estimated to be 3.1eV. p-type doped BeZnTe alloys were grown using an RF-radical nitrogen source. A high hole concentration of 4.8 x 10(18) cm(-3) was obtained for a Be0.4Zn0.6Te sample with a wide bandgap of 2.97eV. These results suggest that BeZnTe is very promising for p-cladding layer materials in short wavelength II-VI laser diodes. (C) 2000 Elsevier Science B.V. All rights reserved.

We report the wavelength control of the arrayed waveguide using MOVPE selective area growth. The asymmetric mask pattern, which placed the wide mask next to the one-side-arrayed waveguide, resulted in the gradient change of the bandgap wavelength in array waveguides. The wavelength in each waveguide was found to be linearly changed and clearly dependent on the wide mask width Ww. A 100 nm photoluminescence peak wavelength shift in the arrayed waveguide was achieved for a 50 μm asymmetric mask pattern, while maintaining linearly shifted profiles.

A new type of optical deflector with a graded refractive index region is proposed. For this device, two types of structure, a multielectrode type and a comblike electrode type, have been numerically analyzed using the finite difference beam propagation method to show results :such as the dependence of the deflection angle and the deflection efficiency on the structure. We fabricated this optical deflector using a GaInAs/InP MQW structure, and we confirmed the fundamental optical deflection and the wavelength dependence of the device. (C) 1999 Scripta Technica.

Superlattice quasi-quaternaries (SL-QQs), consisting of MgSe/ZnSeTe short-period superlattices, were grown on InP substrates by molecular beam epitaxy with nitrogen p-doping. By changing the Mg composition (i.e., the layer thickness ratio of MgSe in the superlattice) from 0 to 0.76, the photoluminescence peak energy at 15 K increased from 2.11 to 7.68 eV. The N-doping of MgSe/ZnSeTe SL-QQs was performed by two processes, that is by the modulation-doping into ZnSeTe and by the all-doping. For the modulation-doping, a hole concentration of over 1 x 10(18) cm(-3) was obtained for Mg composition of less than 0.14, with decreased monotonically with increasing Mg composition. The hole concentration increased by changing the doping process from the modulation-doping to the ail-doping. Far example, the hole concentration increased from 1 x 10(15) to 3 x 10(17) cm(-3) for Mg composition of 0.4. ZnCdSe/MgZnCdSe(Te) light emitting diodes (LEDs) were fabricated using MgSe/ZnSeTe SL-QQs as p-cladding layers having yellow emissions around 577 nm at 77 K.

The gate-length dependencies of the optical response characteristics in an optically controlled metal oxide semiconductor field effect transistor (MOSFET) have been measured. This device was fabricated as an integrated structure of the absorption region anti MOSFET region using the direct wafer-bonding technique. By reducing the gate length of the MOSFET region, the transconductance of the FET channel was increased, and a high current modulation and responsivity was obtained by irradiation of 1.5 mu m wavelength light.

We have demonstrated a novel integrated photo- detector on Si large-scale integration circuits, This device integrated the light absorption region on the gate of metal-oxide-semiconductor field-effect transistor (MOSFET), and the long wavelength light controls the current of MOSFET. The GaInAs-InP multiple-quantum-well absorption region and SiO2 of the MOSFET were directly bonded, From the experimental results, we confirmed that the light-controlled current was increased by shortening the gate length of the MOSFET, and that an 1850 A/W responsivity was obtained in a 3.5-mu m gate length device using an irradiation of 1,5-mu m wavelength light.

屈折率が傾斜するように分布させた構造の光偏向器を提案した. この光偏向器を実現するための構造として, 多電極型と櫛型電極の二つの構造について, ビーム伝搬法を用いた数値解析を行い, 偏向角, 偏向効率等の構造依存性を明らかにした. そして実際にGaInAs/InP多重量子井戸構造をもとに光偏向器を試作し, 電界印加による基本的な光偏向動作と入射光波長依存性を確認した.

New type optical deflector with graded refractive index region has proposed. For this device, two types structure that are multi electrode type and comb like electrode type have been numerical analyzed using Finite Difference Beam Propagation Method, and have shown the structural dependence on the deflection angle and the deflection efficiency, etc. We fabricated this optical deflector using GaInAs/InP MQW structure, and we confirmed the fundamental optical deflection and the wavelength dependence of the device.

High on-off ratio and high responsivity was obtained in a novel integrated optically controlled HEMT, The integrated structure of the device was composed of a p-i-n photodiode region and a HEMT region, These two regions were bonded using direct wafer bonding technique, When a laser light with a wavelength of 1.55 mu m was irradiated on the absorption region, on-off ratio of 12 dB and a responsivity of more than 300 A/W was obtained, This device is very attractive as the high efficiency optoelectronic (OE) transformer directly integrated on the LSI circuits.

ZnCdSe/MgZnCdSe multiple quantum well (MQW) devices were fabricated on InP substrates by molecular beam epitaxy, and quantum-confined Stark effect (QCSE) in the devices were investigated by measurements of reflectance variations at the top surface and absorption coefficient variations in the MQW region with changing applied voltage at room temperature. As a result, remarkable reflectance variations were observed near 587 nm wavelength, accompanied by red shifts of the transition wavelength with increasing applied voltage. A maximum reflectance variation of 5.2% was obtained under the applied voltage of -7.5 V (the electric field of 1.9 x 10(5) V/cm). From the electromagnetic analysis of the device structure. the refractive index variation of 2.4% per well in the MQW was theoretically estimated for the maximum reflectance variation. (C) 1998 Elsevier Science B.V. All rights reserved.

For the first time, high responsivity was obtained from an integrated optically controlled metal-oxide semiconductor field-effect transistor using the direct wafer bonding technique, The integrated structure of the device was composed of an absorption p-i-n photodiode region and a MOSFET, These two regions were bonded using the SiO2-InP direct wafer bonding technique, When a laser light with a wavelength of 1.50 mu m was irradiated on the absorption region, a responsivity of more than 280 A/W was obtained, This is the largest responsivity in an integrated long-wavelength photoreceiver on a Si substrate, This device modulates MOSFET's current by changing the electric field in the absorption region.

我々は光スイッチにないランダムアクセス性に優れた光偏向素子の研究を行っている。これまで理論解析を通じて屈折率分布型の光偏向素子の提案を行ってきた。今回、この構造を持つGaInAsP/InP MQW構造導波路型光偏向素子の試作を行い、その偏向特性を測定した。試作した素子はGaInAsP/InP MQW基板を用い、光入射部である幅5[μm]のリッジ型導波路構造を形成した後に、偏向器部分である幅3[μm]、長さ100[μm]の3本からなる屈折率分布領域を形成し、その先はスラブ導波路領域となっている。偏向器部分には異なる長さの電極を形成し、これに電界を印加することによって屈折率分布が生じ、入射光が偏向されるものである。波長1.46[μm]・0.3[mW]の光を入射し、3本の電極にそれぞれ逆バイアス2[V]印加した時、7[μm]偏向した。これは、偏向角1度に相当する結果である。

An optically controlled field-effect transistor (FET) in which the GaAs FET region and the GaInAs/InP light absorption region were directly bonded is demonstrated. This device offers high optical-to-electrical conversion efficiency. In this work, we report the electrical and optical characteristics of this device based on the direct wafer bonding technique. The bonding temperature dependence on the device characteristics and responsivity characteristics were also measured. As a result, we achieved a high responsivity of more than 150 A/W.

本研究ではInP基板上に格子整合するII-VI族MgZnCdSe系混晶を用いた光変調器の作製を目指している.今回,InP基板に格子整合するZnCdSe/MgZnCdSe多重量子井戸を分子線エピタキシー法により成長し,その量子閉じ込めシュタルク効果(QCSE)を評価したので報告する.この量子井戸構造に電界を印加した時の反射スペクトルを測定したところ,1.87x10^5V/cmの電界印加時に-6.3%の反射率変化が観測された.この値は-3.4%の屈折率変化に相当し,エキシトン効果に起因するものと考えられる.これらのII-VI族特有の大きなエキシトン効果を用いれば,高い消光比を持つ光変調器の実現が期待できる.そこで,屈折率変化層の上下面に多層膜反射鏡を持つファブリペロー型光変調器の設計を行い,消光比や挿入損失等の性能を理論的に見積った.さらにMgZnCdSe多層膜反射鏡を試作し,580nm 等の波長帯において98.0%の反射率を得た.

The drain-to-source current of a metal-oxide semiconductor field-effect transistor (MOSFET) was controlled by long-wavelength laser light for the first time. The device studied was composed of an absorption region and a MOSFET, and these two regions were bonded by polyimide. When the voltage was applied to the absorption region, it shelved the normal operation of a MOSFET. When the laser light with a wavelength of 1.48 mu m was irradiated on to the absorption region, a responsivity of more than 100 A/W was achieved. This device modulates the current of the MOSFET by changing the electric field in the absorption region, and it has the possibility of high-speed operation up to 60 GHz.

Si基板上に集積化された長波長光検出器である光制御MOSFETを異種半導体基板の直接貼付技術を用いて試作、その光応答特性を測定した。光制御MOSFETは光入射によって起こる光吸収領域の電位変化を利用してMOSFETのソース-ドレイン電流を制御するものである。その応答速度は光吸収領域、およびMOSFETの応答速度に依存し、数+GHzの高速下での使用が可能である。直接貼付技術を用いることによって従来の光制御MOSFETより特性の改善が行われ、測定の結果、入射光波長λ=1.50μmにおいて最大変調電流量ΔI_<DS>=560μA、最大光変調電圧ΔV_<PS>=0.4V、最大応答感度R=288A/Wを得た。

An optically controlled field-effect transistor (FET) in which the GaAs FET region and the GaInAs/InP light absorption region were directly bonded was demonstrated. The temperature dependence of the direct bonding and its effect on the performance of the optically controlled FET were examined. A maximum current modulation rate of 60% and a responsivity of more than 150(A/W) were obtained.

異種半導体基板の直接貼付技術を用いて光制御FETの試作を行った。このデバイスは光吸収領域とFET領域から構成され、1.55μm光の入射により、FETのドレインーソース電流を変調制御するものである。今回、貼付プロセスにおけるアニール温度を620、660、700℃にて素子の試作を行い、光応答特性に対する貼付温度依存性を測定した。また、入射光強度依存性に関しても測定し、最大応答感度R=151.8(A/W)(Pm=1μW)を得た。