Norikazu Takado

Vertical to surface transmission electrophotonic device with selectable output light channels

A photoeletronic bistable device with selectable light output channels has been fabricated for implementation in photonic switching and processing systems. The device is a variation of the vertical to surface transmission electrophotonic device. Output in the stimulated light emission mode was successfully obtained from different waveguide channels by external electronic switching. Output channels could be switched at a rate of 400 Mb/s. The potential versatility of this device has been experimentally confirmed in programmable or switchable optical interconnections.

An AlGaAs laser with high-quality dry etched mirrors fabricated using an ultrahigh vacuum in situ dry etching and deposition processing system

Highly reliable AlGaAs lasers with dry etched mirrors have been successfully fabricated with an ultrahigh-vacuum in situ processing system, equipped with reactive ion-beam etching (RIBE) and dielectric film deposition chambers. Etched mirror surfaces are protected against air-exposure contamination and nonvolatile-reaction-products adsorption with in situ Al/sub 2/O/sub 3/ passivation subsequent to the CI/sub 2/ RIBE mirror formation. Ion-bombardment-induced damage is repaired by thermal annealing. The annealing effect is enhanced by a contamination-free interface between the etched mirror surface and Al/sub 2/O/sub 3/ passivation film. The lasers exhibit an increase in catastrophic optical damage (COD) level and long-life operation. Their COD levels are twice as high as that for as-etched lasers and are almost the same as those for conventional cleaved lasers. >

Chlorine-Based Smooth Reactive Ion Beam Etching of Indium-Containing III-V Compound Semiconductor

Very smooth and vertical etching of InP by Cl2 reactive ion beam etching has been achieved under high temperature (≈200°C), high ion energy (≈1 keV) and low Cl2 pressure (~10-5 Torr). The roughness is estimated to be a few nm by scanning tunneling microscopy and no contamination except for Cl was observed by in situ Auger electron spectroscopy. Under these etching conditions, the etched depth is precisely controlled (σ=22 nm) by simply monitoring the electrode curtent of the ion accelerating grid. Other III-V compound semiconductors, such as GaAs, InGaAs, AlGaInP and InAlAs have also been etched smoothly and vertically. Multilayers of these materials, such as InP/InGaAsP, AlGaInP/GaInP, and InAlAs/InGaAs/InP have been etched without steps between the layers on the sidewalls.

Surface‐emitting GaAs/AlGaAs lasers with dry‐etched 45° total reflection mirrors

Surface‐emitting GaAs/AlGaAs lasers with 45° total reflection mirrors have been successfully produced using a 45° tilted reactive ion beam etching technique. The ratio of surface‐emitted light output power to edge‐emitted light output power was obtained at values as high as 77%. The total reflection mirror was formed within 1° of the desired precise 45° angle. This type of surface‐emitting laser is promising for optoelectronic integrated circuits because of the simplicity of its structure and fabrication.

In situ electron beam patterning for GaAs using electron‐cyclotron‐resonance plasma‐formed oxide mask and Cl2 gas etching

A new in situ fabrication process for GaAs is developed. In this process, electron‐ cyclotron‐resonance oxygen plasma is used for the first time to form an oxide mask for Cl2 gas etching. Using this technique, the time and oxygen gas pressure required for the oxidation are drastically reduced, compared to other oxidation methods. Line patterns with submicron width are successfully fabricated by partial modification of the oxide mask by electron beam irradiation and subsequent Cl2 gas etching.

Very Low Threshold AlGaAs/GaAs Quantum Well Lasers Fabricated by Self-Aligned Impurity Induced Disordering

Threshold current as low as 1.2 mA has been achieved in GaAs/AlGaAs quantum well (QW) laser diodes. The low threshold current reflects the high quality of the QW crystal and the low level of leakage current attained in the buried heterostructure. This heterostructure was fabricated with a novel self-aligned mesa etching and Si diffusion process on a molecular beam epitaxy grown planer QW structure. Both the low threshold current and the precisely controllable fabrication process make these lasers quite suitable for optoelectronic integration.

Electron Beam Excited GaAs Maskless Etching Using C12 Nozzle Installed FIB/EB Combined System

We have developed a new fine-beam assisted GaAs maskless etching system capable of nanofabrication; a focused ion beam (FIB) and electron beam (EB) combined etching system with a reactive gas nozzle. In this FIB/EB combined system, EB excited GaAs etching was successfully performed by irradiating Cl2 gas on a temperature-controlled substrate. 5KeV EB was raster-scanned in a 100pm X 20pm rectangular pattern on a GaAs surface. With special care to remove the native oxide layer, spatially selective etching was also confirmed on a cleaned GaAs surface by controlling the Cl2 pressure.

In situ negative‐type patterning of a GaAs/AlGaAs quantum well using electron beam‐induced modification of an InGaAs epitaxial layer mask in Cl2 gas

A GaAs/AlGaAs quantum well structure is in situ patterned by irradiating a thin (50 A) epitaxial In0.2Ga0.8As mask layer with an electron beam (EB) while exposing the mask to Cl2 gas. This simultaneous EB/Cl2 exposure increases the resistance of the mask to Cl2 etching. However, the parts of the mask only exposed to Cl2 are easily etched off, resulting in a negative‐type pattern formation. The etching resistance of the EB/Cl2‐exposed area depends on the In content in the InGaAs mask. Possible causes of this are discussed. Using this method, a GaAs/AlGaAs quantum well is fabricated into a dot‐matrix pattern.