下村 和彦

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。

連続的に光の偏向角を変えることのできる新しい構造の光偏向器を提案する。この構造であれば2次元的に屈折率を分布させることによって比較的容易に面型光偏向器にすることが可能である。我々は、このデバイスの作製の設計指針を得るためにFD-BPMを用いて特性の構造依存性と材料依存性を明らかにした。そして最適構造で偏向角6.5°、偏向効率84%という結果を得た。また、屈折率変化を制御することで、高い偏向効率を保ちつつ偏向角を自由に制御できることが分かった。

A new type optically-controlled field-effect transistor was demonstrated. This device was composed of GaAs material system for the FET region and GaInAs/InP material system for the absorption region, and these regions were electrically isolated by polyimide and SiO2. When 1.55 mum wavelength light entered the absorption region, about 120 muA of source-to-drain current was modulated due to the field-screening effect.

In this article we report theoretical as well as experimental studies of the electric-field-induced refractive index change in InGaAs/InP quantum-well structures, viz., quantum-film, quantum-wire, and quantum-box structures. The refractive index change, easily measured using a Mach-Zehnder interferometer setup, was around 1%, 4%, and 7% in quantum film, quantum wire, and quantum box, respectively, in the longer-wavelength region corresponding to the positive refractive index change peak. Moreover, we will discuss that the refractive index change dependency on the polarization of incident light in a quantum film can be controlled by introducing suitable tensile strain in it. It was found that for a well width of II nm, 0.3% tensile strain should be induced to obtain polarization-independent refractive index change. (C) 1994 John Wiley and Sons, Inc.

Current modulation of an optically-controlled field-effect transistor using the field-screening effect of photogenerated carriers is numerically calculated. When the optical input power is 1 mW, more than 6 mA of current modulation can be obtained in this device.

Semiconductor waveguide optical switches and modulators are reviewed from the view point of material and structure. As material for switches and modulators, effects of both variations of refractive index and absorption are considered. As for the structure of switches and modulators, basic characteristics of devices, including length, speed, and consumption power; are investigated and recent experimental performances are shown. For further improvement of switches and modulators, the importance of low-dimensional quantum-well structures and strained quantum-well structures are pointed out.

A field-effect-type photodetector is proposed. The proposed device is an field-effect-transistor (FET) structure whose output current is controlled by the potential applied to the FET resulting from the field-screening effect of the photogenerated carriers in a diode overlaid on the FET.

We propose a novel integrated-twin-guide (ITG) optical switch with a built-in TIR region to enlarge the spatial separation of output lights, which is suitable for a compact optical switching matrix array. A switching operation was observed in a GaInAsP/InP MQW ITG optical switch utilizing electric-field induced refractive index variation.

We demonstrate a low-drive voltage intersectional waveguide optical switch using 1.6-mu-m GaInAs/InP MQW structure, which was fabricated by only one-step epitaxial growth of MQW structure followed by one-step pattern etching of the waveguide. Extinction ratio at the straight port of 9.9 dB and that at the reflection port of 4.4 dB were obtained at an applied voltage of -4 V.

Operational wavelength range for low insertion loss and high extinction ratio of GaInAs(P)-InP intersectional optical switches consisting of low-dimensional quantum-well structures, such as quantum-box, quantum-wire, and quantum-film structures, is theoretically analyzed. As a result, it is found that superior operation characteristics can be attained with the lower dimensional quantum-well structure, for instance, operational wavelength range of around 10 nm for insertion loss less than 1 dB and extinction ratio higher than 50 dB can be obtained with the device using a quantum-box structure.

An electric-field induced refractive index variation in GaInAs/InP five-layered quantum box structure was observed for the first time. The wavelength dependence of the refractive index variation was also measured to confirm the quantum box effect. The size of the GaInAs/InP quantum box was estimated to be (22-30 nm)2 with the thickness of 7.5 nm, from the spectral property of the field-induced refractive index variation. The maximum value of the refractive index variation in the quantum box was evaluated to be 7% around 1.52-mu-m wavelength at an applied electric field of 8 x 10(4)V/cm.

We propose and analyze a new type of intersectional optical switch using positive refractive index variation in quantum well structure. The switch structure has a built-in refractive index difference in the waveguide, due to which the incident light is reflected to cross port at the OFF state. When the electric field applied to the electrode (ON state), the built-in refractive index difference vanishes by the positive refractive index variation in the quantum well, and the light transmits to straight port. Low insertion loss of lesser than 1 dB and high extinction ratio of more than 20 dB can be obtained at both cross and straight port.

An electric-field induced refractive index variation in GalnAs/InP five-layered quantum box structure was observed for the first time. The wavelength dependence of the refractive index variation was also measured to confirm the quantum box effect. The size of the GalnAs/InP quantum box was estimated to be (22–30 nm)&lt sup&gt 2&lt /sup&gt with the thickness of 7.5 nm, from the spectral property of the field-induced refractive index variation. The maximum value of the refractive index variation in the quantum box was evaluated to be 7% around 1.52 pm wavelength at an applied electric field of 8 x 10&lt sup&gt 4&lt /sup&gt V/cm. © 1991 IEEE

An intersectional optical switch structure with an intersecting angle of 6° was fabricated on OMVPE grown GalnAs/InP MQW wafer (λg = 1.S56/µm), and switching operation using field-induced refractive index variation was successfully demonstrated at the reverse bias voltage of 8 V at 1.6 µm wavelength region. Based on this switching, the field-induced refractive index variation in QW was estimated as around 1 percent. © 1989 IEEE

Large change in the field induced refractive index is achievable by the use of the MQW structures. The property of which can be advantageously utilized to realize high speed external modulators and switches. The GalnAsP/InP MQW structures was prepared by LPE method and the electric field induced absorption was measured. Reflection of light due to refractive index change as well as absorption coefficient change was observed for the first time. Intersectional optical switch based on this change was also fabricated. © 1988 SPIE.